2010微观期末试卷A答案

《微观经济学》课程期末考试试卷（A卷）一选择题1．需求量和价格之所以呈反方向变化，是因为：A．替代效应的作用；B．收入效应的作用；C．上述两种效用同时发生作用；D．以上均不正确。

2.一种商品价格下降对其互补品最直接的影响是：A.互补品的需求曲线向右移动B.互补品的需求曲线向左移动C.互补品的供给曲线向右移动D.互补品的价格上升3.建筑工人工资提高将使：A.新房子供给曲线左移并使房子价格上升B.新房子供给曲线右移并使房子价格下降C.新房子需求曲线左移并使房子价格下降D.新房子需求曲线右移并使房子价格上升4.如果某种商品供给曲线的斜率为正，在保持其余因素不变的条件下，该商品价格的上升将导致：A.供给增加B.供给量增加C.供给减少D.供给量减少5.政府对卖者出售的商品每单位征税3元，假定这种商品的需求价格弹性为零，可以预料价格的上升：A．小于3元B．等于3元C．大于3元D．不能确定6.若X和Y两产品的交叉弹性系数是-1.7，则：A.X和Y是替代品B.X和Y是正常商品C.X和Y是劣质品D.X和Y是互补品7.政府为了扶持农业，对农产品规定了高于其均衡价格的支持价格。

政府为了维持支持价格，应该采取的相应措施是：A.增加对农产品的税收B.实行农产品配给制C.收购过剩的农产品D.对农产品生产者予以补贴8.当LAC曲线下降时，LAC曲线切于SAC曲线的最低点：A．总是对的B．不对C．有时对D．无法判断9. 在完成竞争市场上，厂商短期均衡条件是：A．P=AR B．P=MR C．P=MC D．P=AC10.随着产量的增加，短期平均可变成本：A.先减少后增加B.先增加后减少C.按一定的固定比率在增加D.保持不变11. 假定X、Y的价格Px、Py已定，当MRSxy＞Px/Py时，消费者为达到最大满足，他将：A. 增购X，减少YB. 减少X，增购YC. 同时增购X、YD. 同时减少X、Y12. 假定完全竞争行业内某厂商在目前产量水平上的边际成本、平均成本和平均收益均等于6元，则这家厂商：A．肯定只得到正常利润B．肯定没得到最大利润C．是否得到了最大利润还不能确定D．肯定得到了最少利润13. 一个具有m个厂商的古诺模型中，每个厂商的均衡产量为市场总容量的：A. B. C. D.14. 成本递减行业的长期供给曲线是：A．水平直线B．自左向右上倾斜C．垂直于横轴D．自左向右下倾斜15. 厂商将在何条件下面临停止营业：A. P=A VC B．TR=TVC C．企业总损失等于TFC D．以上都对16．当垄断市场的需求富有弹性时，TR为：A．递增B．递减C．0D．117. 规模收益递减是在下述情况下发生的：A.连续地投入某种生产要素而保持其他生产要素不变B.按相同比例连续增加各种生产要素C.不按比例连续增加各种生产要素D.上述都正确18. 垄断竞争厂商长期均衡点上，长期平均成本曲线处于：A．上升阶段B．下降阶段C．水平阶段D．均有可能19. 垄断竞争厂商实现最大利润的途径是：A．调整价格从而确定相应产量B．品质竞争C．广告竞争D．以上都可能20. 完全竞争市场中厂商总收益曲线的斜率为：A．固定不变B．可变的C．1D．021. 假定玉米市场的需求是缺乏弹性的，玉米的产量等于销售量且等于需求量，恶劣的气候条件使玉米产量下降20%，在这种情况下：A.玉米生产者的收入减少，因为玉米产量下降20%B.玉米生产者的收入增加，因为玉米价格上升低于20%C.玉米生产者的收入增加，因为玉米价格上升超过20%D.玉米生产者的收入减少，因为玉米价格上升低于20%22. 正常利润是：A．经济利润的一部分B．经济成本的一部分C．隐含成本的一部分D．B和C都对23. 预算线反映了：A.消费者的收入约束B.消费者的偏好C.消费者人数D.货币的购买力24. 形成不完全竞争市场的原因是：A.对生产要素的垄断B.法律方面的进入壁垒C.产品差异化D.以上都对25. 经济物品是指：A．有用物品B．稀缺物品C．要用钱购买的物品D．有用且稀缺的物品26. 在某产量水平上，厂商平均成本达到最小，意味着：A.边际成本等于平均成本B.厂商获得最大利润C.厂商获得最小利润D.厂商的超额利润为零27. 下列行业中哪一个最接近完全竞争市场状况：A.医药B.家电C.小麦D.化妆品28. 某行业许多生产者都生产标准化产品，它的需求是：A.无弹性B.单一弹性C.缺乏弹性D.富有弹性29. 若小王消费牛奶和面包时的边际替代率为1/4，即一单位牛奶相当于1/4单位的面包，则：A. 牛奶价格为4，面包价格为1时，小王获得最大效用B. 牛奶价格为1，面包价格为4时，小王获得最大效用C. 牛奶价格为10，面包价格为2时，小王应增加牛奶的消费D. 以上都不对30. 如果一个价格歧视垄断者对学生收取低价格，那么，它就是相信：A.学生的需求是富有弹性的B.学生的需求是缺乏弹性的C.想使学生的需求曲线移动D.学生的购买能力强二、判断题1. 在一个完全竞争行业中，没有一个企业能对产品的市场价格有任何重要的影响。

]《微观经济学》期末试卷A卷及部分答案一、名词解释15分（每小题3分）机会成本，是把该资源投入某一特定用途以后，所放弃的在其他各种可能的用途中所能获得的最大收益。

需求弹性，消费者剩余，边际替代率，在维持效用水平不变的前提下，消费者增加一单位某种商品的消费数量所需要放弃的另一种商品的消费数量，被称为商品的边际替代率。

无差异曲线单项选择题30分（每小题2分）1、以下不是直接影响需求的因素或条件是（D）A、价格；B、偏好；C、收入；D、成本2、当出租车租金上涨后，对公共汽车服务的（B）A、需求下降；B、需求增加；C、需求量下降；D、需求量增加3、若需求曲线富有弹性，其确切的含义是价格上升会引起（A）A、购买者购买量的下降；B、购买者购买量的增加；C、购买者总支出的增加；D、购买者总支出的减少4、已知商品X的价格10元，商品Y的价格是3元，假定消费者有收入100元，他打算购买7单位的X，10单位的Y，这时商品X和Y的边际效用是50和18，如果要获得最大效用，他应该（D）A、停止购买；B、增加Y，减少X ；C、同进增加购买X，Y；D、减少Y，增加X5、如果商品A和商品B是互补的，则A的价格下降将造成（A）A、商品B的需求曲线向右移动；B、商品B的需求曲线向左移动；C、商品A需求曲线向右移动；D、商品A需求曲线向左移动；6、假如一个完全竞争厂商接到的订单价格小于平均成本但大于平均可变成本，它应该是(C)A、停止生产；B、生产且有利润；C、亏损但继续生产；D生产且利润为零7、如果价格下降10%能使买者总支出增加10%，则这种商品的需求量对价格（A）A、富有弹性；B、具有单位弹性；C、缺乏弹性；D、其弹性不能确定8、己知XY两种商品的交叉弹性－0.4，则这两种商品是（C）A、.独立品；B、替代品；C、补充品；D、不能确定9、在完全竞争市场中，厂商短期均衡条件是（C）A、P=AR ；B、P=MR；C、P=MC；D、P=AC10、市场均衡意味着：（D）A、在某一价格水平上供给数量等于需求数量；B、在均衡价格水平上，每一个买者都可以买到想买的数量，每一个卖者都可以卖出想卖的数量；C、价格没有变动的趋势；D、上述答案均正确。

《微观经济学》试卷（ A卷)一、选择题（每小题 2 分，共 20 分。

每题只有一个正确答案，请将答案号填在题后的括符内）1、当汽油的价格上升时，对小汽车的需求量将：( ）A、减少B、保持不变C、增加D、不一定2、均衡价格随着：( ）A、需求与供给的增加而上升B、需求的减少和供给的增加而上升C、需求的增加与供给的减少而上升D、需求与供给的减少而上升3、在市场经济中，减少汽油消费量的最好办法是:（)A、宣传多走路、少坐汽车有益于身体健康B、降低人们的收入水平C、提高汽油的价格D、提高汽车的价格4、政府为了扶持农业,对农产品实行支持价格。

但政府为了维持这个高于均衡价格的支持价格,就必须：（）A、实行农产品配给制B、收购过剩的农产品C、增加对农产品的税收D、给农民补贴5、比较下列四种商品中哪一种商品需求的价格弹性最大：( )A、面粉B、大白菜C、点心D、大米6、你逐渐消费某种商品的过程中（）A、总效用在增加，边际效用在减少B、总效用和边际效用都在增加C、总效用和边际效用都在减少D、总效用减少，边际效用增加7、当其他生产要素不变，而一种生产要素增加时：（)A、总产量会一直增加B、总产量会一直减少C、总产量先增加后减少D、总产量先减少后增加8、下列项目中可称为可变成本的是：( ）A、管理人员的工资B、原材料费用C、厂房和机器设备的折旧D、厂房租金9、当要素市场存在垄断时，不存在厂商对要素的需求曲线，这是因为：（）A、厂商不需要生产要素B、厂商需要生产要素，但由于是垄断，不存在要素的市场价格C、厂商对要素的需求会影响到要素的市场价格，两者之间可能没有一一对应关系D、不一定，因为不同企业、不同市场不一样10、要素需求的关联性是指:( )A、现实经济中，一般厂商生产四大类要素都需要,缺一不可B、厂商按照固定比例确定对各种要素的需求C、厂商对要素的需求与消费者对厂商的产品的需求相关联D、因为不同类型企业对四类要素的需求比例不同，所以不存在所谓的关联性二、填空题(每题 2 分，共 10 分）1、当前世界上的基本经济制度有两种，一种是，一种是。

武汉大学期末考试经济与管理学院微观经济学（A卷）Principles of Microeconomics (Paper A)InstructionYou have two hours to complete this test. Full marks are 100 points.Write your answers on the answer sheet. You can answer your questions either in English or in Chinese. Read the questions carefully before answering them. English-Chinese Dictionary is allowed in this test if it is a published one without any damage on it.Be precise and keep to the point.Good luck!You are required to answer question 1-7.1.(10%) Concepts. Give at least two examples for each concept below:Negative externalities, club goods, implicit costs, cartel, and dominant strategies.2.(10%) Understand rationality assumption. (1) According to the way we define rationalityin the class or in the textbook, are you rational? Explain. (2) On the other hand, the possibility always exist that someone is irrational occasionally.List situations of irrationality and explain.3.(10%) Economists claim that imperfectly competitive firms do not have supply curve. Doyou agree with this theory? Defend.4.(10%) One of economic principles says that rational people often make decisions bycomparing marginal benefits and marginal costs. There are at least three theories about households and firms in the textbook that are consistent with the principle. Show them. 5.(10%) Show that increasing return to scale can be expressed in terms of decreasingaverage cost instead of decreasing marginal cost.(If you cannot do it in mathematics, try to explain in words.)6.(10%) Consider public policy aimed at smoking.(1)Studies indicate that the price elasticity of demand for cigarettes is about 0.4. If a packof cigarettes currently costs $2 and the government wants to reduce smoking by 20%, by how much should it increase the price?(2)If the government permanently increases the price of cigarettes, will the policy have alarger effect on smoking one year from now or five years from now?(3)Studies also find that teenagers have higher price elasticity than do adults. Why mightthis be true?7.(20%) Suppose that a consumer buys two goods, with quantities x and y, and prices p xand p y respectively. And suppose her budget is m and preference is described by u = ln xy.(1)Find her demand for good x as a function of x’s price, y’s price, and her income (m).(2)Are x and y inferior good? Are x and y Giffen good? Why?(3)Can you find the existence of scarcity in this case? No matter what your answer is,let’s assume that there is no scarcity at all, should economics be developed? (Is it justified for economics to exist?)(4)Is rational behavior a basic rule dominating her choice? Why?Hints: marginal utility of x is 1/x and marginal utility of y is 1/y in this preference.You may choose ANY ONE of question 8-9 to anser.8.(20%) Based on market research, a film production company in Ecternia obtains thefollowing information about the demand and production costs of its new DVD:Demand: P =1000 – 10 QCost: C = 100 Q+ 5 Q2Where Q indicates the number of copies sold and P is the price in Ecternian dollars.(1)Find the price and quantity that maximizes the company’s profit.(2)Find the price and quantity that would maximize social welfare.(3)Calculate the deadweight loss from monopoly.(4)Suppose, in addition to the costs above, the director of the film has to be paid. Thecompany is considering four options: A flat fee (固定费用) of 2000 Ecternian dollars;50% of the profits; 150 Ecternian dollars per unit sold; 50% of the revenue. For each option, calculate the profit-maximizing price and quantity. Which, if any, of these compensation schemes would alter the deadweight loss from monopoly? Explain.9.(20%) Show mathematically that imperfectly firms set price as the sum of marginal costand a markup over this marginal cost. Also show that the markup is associated with elasticity of demand. Finally use this result to show that the markup disappears under perfect competition.THE ENDThe Answer10.(10%) Concepts. Give at least two examples for each concept below:Negative externalities, club goods, implicit costs, cartel and dominant strategies.Negative externalities: the exhaust from automobiles, smoking, barking dog, etc.Club goods: cable TV, Un-congested toll road, wireless communication service, etc.Implicit costs: the income you give up as a teacher when you create a business, rent you give up when you use own house as offices, etc.Cartel: OPEC, Labor Union, etc.11.(10%) Understand rationality assumption. (1) According to the way we define rationalityin the class or in the textbook, are you rational? Explain. (2) On the other hand, the possibility always exist that someone is irrational occasionally.List situations of irrationality and explain.(1) The firms always pursue profit maximization; the consumers always pursue utilitymaximization.(2) The irrational will exist for asymmetric information, altruism(利他主义).12.(10%) Economists claim that imperfectly competitive firms do not have supply curve. Doyou agree with this theory? Defend.A supply curves tell us the quantity that firms choose to supply at any given price. Thisconcept makes sense when we are analyzing competitive firms which are price takers. But an imperfectly competitive firm is a price maker to some extent, at least not a pure price taker. It is not meaningful to ask what such a firm would produce at any price because the firm can set the price at the same time it chooses the quantity to supply. An imperfectly competitive firm’s decision about supply quantity is impossible to separate from the demand curve it faces. The shape of the demand curve determines the shape of the marginal revenue curve,which in turn determines the imperfectly competitive firm’s profit-maximizing quantity. But in a perfectly competitive market, supply decision can be analyzed without knowing the demand curve.13.(10%) One of economic principles says that rational people often make decisions bycomparing marginal benefits and marginal costs. There are at least three theories about households and firms in the textbook that are consistent with the principle. Show them.The firm decides the profit-maximizing quantity according to MR=MC;The firm achieves the quantity-maximizing given total cost according to(MP L)/w= (MP K)/rThe consumer decides the optimal combination of commodity according to (MUi/Pi)= (Mj/Pj)=MU Currency14.(10%) Show that increasing return to scale can be expressed in terms of decreasingaverage cost instead of decreasing marginal cost.(If you cannot do it in mathematics, try to explain in words.)Suppose the product function: ),(K L Af Q =, the prices of L and K are w and r respectively, w and r are both constant.This is ),(000K L Af Q =, 000rK wL TC +=,000000000///)(/Q rK Q wL Q rK wL Q TC ATC +=+==∵ The return to scale is increasing.∴ ),()(000xK xL Af Q x =+α,0 α,000rxK wxL C T +=', )/()/()/()(/0000000000Q rK x x Q wL x x Q x rxK wxL Q C T C AT ααα+++=++='='00ATC C AT '15.(10%) Consider public policy aimed at smoking.(4)Studies indicate that the price elasticity of demand for cigarettes is about 0.4. If a pack of cigarettes currently costs $2 and the government wants to reduce smoking by 20%,by how much should it increase the price?(5)If the government permanently increases the price of cigarettes, will the policy have a larger effect on smoking one year from now or five years from now?(6)Studies also find that teenagers have higher price elasticity than do adults. Why might this be true?(1)With a price elasticity of demand of 0.4, reducing the quantity demanded of cigarettes by 20 percent requires a 50 percent increase in price, since 20/50 = 0.4. With the price of cigarettes currently $2, this would require an increase in the price to $3.33 a pack using the midpoint method (note that ($3.33 - $2)/$2.67 = .50).(2)The policy will have a larger effect five years from now than it does one year from now.The elasticity is larger in the long run, since it may take some time for people to reduce their cigarette usage. The habit of smoking is hard to break in the short run.(3)Since teenagers don't have as much income as adults, they are likely to have a higher price elasticity of demand. Also, adults are more likely to be addicted to cigarettes,making it more difficult to reduce their quantity demanded in response to a higher price.16.(20%) Suppose that a consumer buys two goods, with quantities x and y , and prices p x and p y respectively. And suppose her budget is m and preference is described by u = ln xy .(5)Find her demand for good x as a function of x ’s price, y’s price, and her income (m ).(6)Are x and y inferior good? Are x and y Giffen good? Why?(7)Can you find the existence of scarcity in this case? No matter what your answer is,let’s assume that there is no scarcity at all, should economics be developed? (Is it justified for economics to exist?)(8)Is rational behavior a basic rule dominating her choice? Why?Hints: marginal utility of x is 1/x and marginal utility of y is 1/y in this preference.The condition of the consumer’ maximizing utility is yy x x P MU P MU //=x MU x /1= and yMU y /1=So y x P y P x /)/1(/)/1(= (1)The condition of the consumer’ budget constraint is m yP xP y x =+ (2)According to (1) and (2):x P m x 2/=, yP m y 2/=So x and y are not inferior goods, of course they are not Giffen Goods too.You may choose ANY ONE of question 8-9 to answer.17.(20%) Based on market research, a film production company in Ecternia obtains the following information about the demand and production costs of its new DVD:Demand: P =1000 – 10 QCost: C = 100 Q+ 5 Q 2Where Q indicates the number of copies sold and P is the price in Ecternian dollars.(5)Find the price and quantity that maximizes the company’s profit.(6)Find the price and quantity that would maximize social welfare.(7)Calculate the deadweight loss from monopoly.(8)Suppose, in addition to the costs above, the director of the film has to be paid. The company is considering four options: A flat fee (固定费用) of 2000 Ecternian dollars;50% of the profits; 150 Ecternian dollars per unit sold; 50% of the revenue. For each option, calculate the profit-maximizing price and quantity. Which, if any, of these compensation schemes would alter the deadweight loss from monopoly? Explain.QQ Q Q Q P TR 100010)101000(2+-=*-=*=100020/+-==Q dQ dTR MR QdQ dTC MC 10100/+==The condition of Maximizing-Profit: MR=MCSo 30max =Q , 700max =P , 400max =MC When the market is perfectly competitive, the social welfare is maximized, then P=MC QQ 10100101000+=-So 45=optim Q , =perfect P 550The deadweight loss = 0.5*(45-30)*(700-400)=2250a) 200051002++=Q Q TC a , Q MC a 10100+=, 30max =a Q ,700max =a P , the deadweight loss is unchanged.b) The option is not change the condition of maximizing profit, so 30max =b Q , 700max =b P ,the deadweight loss is unchanged.c) Q Q Q TC c 15051002++=, Q MC c 10250+=, 25max =c Q , 750max =c P , the deadweightloss is changed.d) )100010(21510022Q Q Q Q TC d +-++=, 600=d MC , 20max =d Q , 800max =d P , the deadweight loss is changed.18.(20%) Show mathematically that imperfectly firms set price as the sum of marginal cost and a markup over this marginal cost. Also show that the markup is associated with elasticity of demand. Finally use this result to show that the markup disappears under perfect competition.Q dQ dP P dQ Q P d dQ dTR MR MC ∙+=*===)( Q dQ dP MC P ∙-=∴0<dQdP ξ+=∴MC P , 0)(>∙-=Q dQ dP ξQ P dP dQ e d ∙-= de P Q dQ dP =∙-∴d e PMC P +=∴de MCP 11+=∴When the market is perfect competition, the +∞=d e , and P=MC。