武汉大学 微观经济学 模拟试题3
姓名:
学号:
成绩:
1.. Explain why each of the following statements about profit-maximizing competitive firms is incorrect. Restate each one correctly. (10 score)
a) A competitive firm will produce output up to the point where price equals average variable
cost.
b) A firm’s shutdown point comes where price is less than minimum average cost.
c) A firm’s supply curve depends only on its marginal cost. Any other cost concept is irrelevant
for supply decisions.
d) The P=MC rule for competitive industries holds for upward-sloping, horizontal, and
downward-sloping MC curves.
e) The competitive firm sets price equal to marginal cost. 2. Explain the fallacies in each of the following: (10 score)
a) Average costs are minimized when marginal costs are at their lowest point.
b) Because fixed costs never change, average fixed cost is a constant for each level of output. c) Average cost is rising whenever marginal cost is rising.
d) The opportunity cost of drilling for oil in Yosemite Park is zero because no firm produces
anything there.
e) A firm minimizes costs when it spends the same amount on each input.
3.. Explain why each of the following is false, (10 score)
a) A freeze in Brazil’s coffee-growing region will lower the price of coffee. b) ―Protecting ‖American textile manufacturers from Chinese clothing imports will lower
clothing price in the United States.
c) The rapid increase in college tuitions will lower the demand for college.
d) The war against drugs, with increased interdiction of imported cocaine, will lower the price
of domestically produced marijuana.
4..For each of the following, explain whether quantity demanded changes because of a demand shift or a price change, and draw a diagram to illustrate your answer. (10 score) a) As a result of decreased military spending, the price of Army boots falls. b) Fish prices fall after the pope allows Catholics to eat meat on Friday. c) An increase in gasoline taxes lowers the consumption of gasoline.
d) After the Black Death struck Europe in the fourteenth century, wages rose.
5. Using a supply-and-demand diagram, illustrate the impact of each of the following on price and quantity demanded: (10 score)
a) Improvements in transportation lower the costs of importing oil into the United States in the
1960s.
b) After the 1973 war, oil producers cut oil production sharply. c) After 1980s, smaller automobiles get more miles per gallon.
d) A record-bearing cold winter in 1995-1996 unexpected raises the demand for heating oil. e) A global economic recovery in 1999-2000 led to a sharp upturn in oil prices.
6.. Consider a competitive market for apartments. What would be the effect on the equilibrium output and price after the following changes (other things held equal)? In each case, explain your answer using supply and demand. (10 score)
a) A rise in the income of consumers
b) A $10-per-month tax on apartment rentals
c) A government edict saying apartments could not rent for more than $200 per month. d) A new construction technique allows apartments to be built at half the cost. e) A 20 percent increase in the wages of construction workers. 7..“好收成往往降低农民的收入”，试用供给—需求图形解释这一命题。 ( ―A good harvest will generally lower the income of farmers.‖ Illustrate this proposition using a supply-and-demand diagram.) (10 分)
8、什么是寡头？叙述囚徒困境的故事？囚徒困境告诉我们关于寡头的什么道理？（10分）
9、什么是劳动力的边际产量？什么是劳动力的边际产量值？一个竞争性的、利润最大化的厂商如何确定雇用多少劳动力？（10分）
10、我们知道，完全竞争厂商的供给曲线是向上倾斜的。请问是否可能存在着一条向下倾斜的供给曲线，为什么？（10分）
模拟试题3答案
1.. Explain why each of the following statements about profit-maximizing competitive firms is incorrect. Restate each one correctly. (10 score)
f) A competitive firm will produce output up to the point where price equals average variable
cost. (Correct answer: A competitive firm will produce output up to the point where price equals marginal cost.) g) A firm’s shutdown point comes where price is less than minimum average cost. (Correct answer: A firm’s shutdown point comes where price is less than minimum average variable cost.) h) A firm’s supply curve depends only on its marginal cost. Any other cost concept is irrelevant
for supply decisions. (Correct answer: A firm’s supply curve depends only on its marginal cost above the shutdown price where MC=AVC..) i) The P=MC rule for competitive industries holds for upward-sloping, horizontal, and
downward-sloping MC curves. (Correct answer: The rule does not hold for downward-sloping MC.) j) The competitive firm sets price equal to marginal cost. (Correct answer: The competitive firm chooses output to set marginal cost equal to price. It has no discretion over price.) 2. Explain the fallacies in each of the following: (10 score)
f) Average costs are minimized when marginal costs are at their lowest point. (Correct: Average costs are minimized when marginal costs equals average costs; Ac is falling where Mc is minimized) g) Because fixed costs never change, average fixed cost is a constant for each level of output.
(Correct: AFC=FC/Q; FC is fixed so as output increase AFC falls.) h) Average cost is rising whenever marginal cost is rising. (Correct: AC is rising whenever MC> AC; AC is falling whenever MC< AC, even if MC is rising) i) The opportunity cost of drilling for oil in Yosemite Park is zero because no firm produces
anything there. (Correct: The absence of a market does not imply the absence of value) j) A firm minimizes costs when it spends the same amount on each input. (Correct: A firm minimizes costs when the ratios of marginal product to input price are equal for all inputs.) 3.. Explain why each of the following is false, (10 score)
e) A freeze in Brazil’s coffee-growing region will lower (correct answer: increase) the price of
coffee.
f)
―Protecting ‖American textile manufacturers from Chinese clothing imports will lower (correct answer: increase) clothing price in the United States.
g) The rapid increase in college tuitions will lower the demand for college.( The rapid increase
in college tuitions reflect increase in demand for college; or, Increase in demand for college will push up the rapid increase in college tuitions)
h) The war against drugs, with increased interdiction of imported cocaine, will lower (correct answer: increase) the price of domestically produced marijuana.
武汉大学 微观经济学 模拟试题4
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成绩: 一、计算题
1、假设过桥旅游的需求为：Y=1,000,000 – 50,000P, 这里，Y为过桥旅游的数量，P为过桥费（用美元计算）。当过桥费为$0, $1, 和 $20时，请计算消费者的剩余？ ( 15 score )
2、竞争厂商实现利润最大化的均衡条件？当竞争性厂商把其产量提高一倍，该厂商的产品的销售价格和总收益会发生什么变化？（15分）
二、图形分析题（从3题中任意选择做2题）
3.Show that a cartel that sets a quantity target (the inelastic supply curve) will experience more volatile prices if demand is price-inelastic than if demand is price-elastic when: (1) the demand curve shifts horizontally by a certain quantity (a forecasting error) or (2) when there is a shift in the supply curve (say due to cheating by a cartel member). (15 score)
4. Consider what would happen if a tariff of 80% were imposed on imported automobiles. Show the impact of this tariff on the supply and the demand, and on the equilibrium price and quantity of Chinese automobiles. Explain why Chinese auto companies and autoworkers often support import restraints on automobiles. (15 score)
5..Larry, Curly, and Moe run the only saloon in town. Larry wants to sell as many drinks as possible without losing money. Curly wants the saloon to bring in as much revenue as possible. Moe wants to make the largest possible profits. Using a single diagram of the saloon’s demand curve and its cost curves, show the price and quantity combinations favored by each of the three partners. Explain. (15 score)
一、简答题（每题10分）
6、什么是最高限价和最低限价？哪一个会导致短缺？哪一个会导致过剩？为什么？为什么经济学家们通常反对价格控制？ 7、通讯员候林斯曾经说过：“消费者并没有从低价格的进口中获得益处，因为只要看一眼邮购的商品类别，你就会发现消费者恰好支付了同样的商品价格，而无论它是美国生产的还是进口的。”请对这句话加以评论。
一、多项选择: (共20分，其中每小题4分.)
﹍﹍﹍﹍1．消费者的无差异曲线具有的特点是
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A具有正斜率；B斜率递减；C任意两条不相交；D位于右上方的无差异曲线具有较高的效用水平
﹍﹍﹍﹍2．商品X对商品Y的边际替代率MRSXY小于X和Y的价格比PX/P则该消Y，费者
A获得了最大效用；B应该增加X的消费，减少Y的消费 C减少X的消费，增加Y的消费；D消费者没有获得最大效用
﹍﹍﹍﹍3．在同一条无差异曲线上（代表商品X和商品Y的组合） A消费商品X获得的总效用等于消费商品Y获得的总效用 B消费商品X获得的边际效用等于消费商品Y获得的边际效用
C．?X?MUX??Y?MUY； D曲线上任两点对应的消费品组合（X，Y）所能带来的总效用相等
﹍﹍﹍﹍4．边际收益递减规律发生作用的前提是() A存在技术进步； B生产技术水平不变；
C具有两种以上可变要素的生产； D只有一种可变要素的生产 ﹍﹍﹍﹍5．在LAC曲线下降的区域，
ALAC?SAC；B SAC的最低点在LAC上；C LAC与各条SAC相切于SAC最低点的左侧；D LAC是SAC最低点的连线.
多项选择题的参考答案：
﹍﹍﹍﹍1．消费者的无差异曲线具有的特点是
A具有正斜率；B斜率递减；C任意两条不相交；D位于右上方的无差异曲线具有较高的效用水平
﹍﹍﹍﹍2．商品X对商品Y的边际替代率MRSXY小于X和Y的价格比PX/P则该消Y，费者
A获得了最大效用；B应该增加X的消费，减少Y的消费 C减少X的消费，增加Y的消费；D消费者没有获得最大效用 ﹍﹍﹍﹍3．在同一条无差异曲线上（代表商品X和商品Y的组合） A消费商品X获得的总效用等于消费商品Y获得的总效用 B消费商品X获得的边际效用等于消费商品Y获得的边际效用
C．?X?MUX??Y?MUY； D曲线上任两点对应的消费品组合（X，Y）所能带来的总效用相等
﹍﹍﹍﹍4．边际收益递减规律发生作用的前提是() A存在技术进步； B生产技术水平不变；
C具有两种以上可变要素的生产； D只有一种可变要素的生产 ﹍﹍﹍﹍5．在LAC曲线下降的区域，
ALAC?SAC；B SAC的最低点在LAC上；C LAC与各条SAC相切于SAC最低点的左侧；D LAC是SAC最低点的连线.
