一、先判断正确与否，如果是错误的把它改正过来( 每小题2分)
1)A freeze in Brazil’s coffee-growing region will lower the price of coffee.
2)“Protecting ”American textile manufacturers from Chinese clothing imports will lower clothing price in the U.S.
3)The rapid increase in college tuitions will lower the demand for college.
4)The war against drugs, with increased interdiction of imported cocaine, will lower the price of domestically produced marijuana.
5)A competitive firm will produce output up to the point where price equals average variable cost.
6)A firm’s shutdown point comes where price is less than minimum average cost.
7)A firm’s supply curve depends only on its marginal cost.
8)The P=MC rule for competitive industries holds for upward-sloping, horizontal, and downward-sloping MC curves.
9)Average costs are minimized when marginal costs are at their lowest point.
10)A firm minimizes costs when it spends the same amount on each input.
二、计算题
1)Suppose that business travelers and vacationers have the following demand for airline tickets from Beijing to Tibet: As the price of tickets rises from $200 to $250, what is the price elasticity of demand for (i) business travelers and (ii) vacationers?
价格 | 需求量 (Business travelers) | 需求量 (Vacationers) |
$ 150 | 2100 | 1000 |
200 | 2000 | 800 |
250 | 1900 | 600 |
300 | 1800 | 400 |
2)Two driver--Tom and Jerry—each drive up to a gas station. Before looking at the price, each places an order. Tom says, “I’d like 10 gallons of gas.” Jerry says, “I’d like $10 of gas.” What is each driver’s price elasticity of demand?
三、画图并用文字解释题
1.An interesting application of supply and demand to addictive substances compares alternative techniques for supply restriction. For this problem, assume that the demand for addictive substances is inelastic.
a)One approach (used today for heroin and cocaine and for alcohol during Prohibition) is to reduce supply at the nation’s borders. Show how this raises price and increases the total income of the suppliers in the drug industry.
b)An alternative approach (followed today for tobacco and alcohol) is to tax the goods heavily. Using the tax apparatus, show how this reduces the total income of the suppliers in the drug industry.
2.The government decides to tax a monopolist at a constant rate of $x per unit. Show the impact upon output and price. Is the post-tax equilibrium closer to or further from the ideal equilibrium of P=MC?
【参考答案】
一、先判断正确与否，如果是错误的把它改正过来( 每小题2分)
1)A freeze in Brazil’s coffee-growing region will increase the price of coffee.
2)“Protecting ”American textile manufacturers from Chinese clothing imports will increaseclothing price in the U.S.
3)The rapid increase in college tuitions will show shift rightward in the demand for college.
4)The war against drugs, with increased interdiction of imported cocaine, will increase the price of domestically produced marijuana.
5)A competitive firm will produce output up to the point where price equals marginal cost (P=MC).
6)A firm’s shutdown point comes where price is less than minimum average variable cost.
7)A firm’s supply curve in the short-run depends only on its marginal cost curve above minimum average variable cost. (或者改正：A firm’s supply curve in the long-run depends only on its marginal cost curve above minimum average cost.)
8)The P=MC rule for competitive industries holds for upward-sloping, horizontal MC curves.
9)Average costs are minimized when marginal cost curve crosses average cost curve.
10)A firm minimizes costs when it spends the last dollar on each input is the same.
二、计算题
1.
提示：根据中点法的计算公式进行
2.Two--Tom and Jerry—each drive up to a gas station. Before looking at the price, each places an order. Tom says, “I’d like 10 gallons of gas.” Jerry says, “I’d like $10 of gas.” What is each driver’s price elasticity of demand?
答：（1）汤姆的需求价格弹性为零。因为不论汽油的价格如何变化，汤姆始终只购买10加仑的汽油，也就是说汤姆的数量变化为零，即△q＝0。
首先，根据中点法的需求价格弹性公式，分子为零（△q＝0），最终的需求价格弹性为零。
另一种方法：根据点弹性的需求价格弹性公式，计算结果也同样为零。
因此，汤姆的需求价格弹性为零。
(2) 方法1 (Using mid-point approach, or arc-elasticity)：
杰瑞的需求价格为1。
杰瑞始终花10美元购买汽油，始终有如下公式成立：
三、划图并用文字解释题
1．
a) 从国家的国界处削减对上瘾物品的供给，正如图形”a”所示，供给从S向左移动到S '，当需求不发生变化时，新的供给与原需求曲线相交于E点，新的均衡点E点与原有的均衡点B点相比，新的均衡价格从OA上涨到OD，均衡数量从OC减少到OF。
上瘾物品供给商的收入从面积OABC增加到ODEF。从图形可以看出，除公共面积OANF外，面积ADEN显然要大于面积NBCF。因为面积代表的就是供给商的收入，所以供给商的收入增长了。
b)如果对供给商征收重税，如图形“b”所示，因为税收使供给成本供给上升，供给曲线从S向上移动到S"，新的供给曲线与原有的需求曲线相交于E点，此时新的均衡价格OD高于原均衡价格OA，新的均衡数量OF小于原均衡数量OC。
如果政府对上瘾物品按照每单位征收$x的税收的话，单位税率乘以均衡数量的面积MNED就是政府的税收收入。
上瘾物品的供应商实际获得的收入是面积OMNF，大大小于原有的面积OABC，从图形中可以很直观地看出来。
消费者的实际支出从原有的面积OABC增长到ODEF，因为价格上涨的幅度要大于数量减少的幅度。
2.
从下图中可以看出，当政府决定对垄断者征收每单位x 美元的税率，
它必然引起垄断价格的上升，如图形中所示，从p上升到p'。
垄断者的均衡数量下降，如图形所示，从q下降到q'。
竞争条件下的理想均衡满足P=MC，均衡数量为图形所示的q*。从图形可以看出，税后的
均衡远离P=MC的理想条件下的均衡。
