经济学基础 第一次作业 09 答案

西方经济学第一次作业

1. 假设大学里篮球票的价格是由市场力量决定的。现在，需求与供给表如下：

价格(美元) 需求量(张) 供给量(张) 4 10000 8000 8 8000 8000 12 6000 8000 16 4000 8000

20 2000 8000

a．画出需求曲线和供给曲线。这条供给曲线有什么不寻常之处？为什么会是这样的？ b．篮球票的均衡价格和均衡数量是多少？

c．明年你们大学计划共增加5000名学生。增加的学生的需求表如下： 价格(美元) 需求量(张) 4 4000 8 3000 12 2000 16 1000 20 0

现在把原来的需求表与新生的需求表加在一起计算整个大学的新需求表。新的均衡价格和均衡数量是多少？

a.

As Figure 2-25 shows, the supply curve is vertical. The constant supply makes sense because the basketball arena

has a fixed number of seats no matter what the price.

Figure 2-25

b.

c.

Quantity supplied equals quantity demanded at a price of $8. The equilibrium quantity is 8,000 tickets.

Price $ 4 8 12 16 20

Quantity Demanded 14,000 11,000 8,000 5,000 2,000 Quantity Supplied 8,000 8,000 8,000 8,000 8,000 The new equilibrium price will be $12, which equates quantity demanded to quantity supplied. The equilibrium quantity is 8,000 tickets.

2. 假设公务乘客和度假乘客对从纽约到波士顿之间民航机票的需求如下： 价格 需求量 需求量 (美元) (公务乘客) (度假乘客) 150 2100 1000 200 2000 800 250 1900 600 300 1800 400

a．当票价从200美元上升到250美元时，公务乘客的需求价格弹性为多少？度假乘客的需求价格弹性为多少？(用中点法计算。)

b．为什么度假乘客与公务乘客的需求价格弹性不同？

a.

For business travelers, the price elasticity of demand when the price of tickets rises from $200 to $250 is [(2,000 -

1,900)/1,950]/[(250 - 200)/225] = 3/13 = 0.23. For vacationers, the price elasticity of demand when the price of tickets rises from $200 to $250 is [(800 - 600)/700] / [(250 - 200)/225] = 9/7 = 1.29.

b.

The price elasticity of demand for vacationers is higher than the elasticity for business travelers because vacationers can more easily choose a different mode of transportation (like driving or taking the train). Business travelers are less likely to do so since time is more important to them and their schedules are less adaptable.

3. 这是一个热天，Bert口干舌燥。下面是他对一瓶水的评价：

对第一瓶水的评价 7美元 对第二瓶水的评价 5美元 对第三瓶水的评价 3美元 对第四瓶水的评价 1美元

a．根据以上信息推导出Bert的需求表。画出他对瓶装水的需求曲线。 b．如果一瓶水的价格是4美元，Bert会买多少瓶水？Bert从他的购买中得到了多少消费者剩余？在你的图形中标出Bert的消费者剩余。

c．如果价格下降到2美元，需求量会有何变化？Bert的消费者剩余会有何变化？用你的图形说明这些变化。

a. Bert’s demand schedule is:

Price More than $7 $5 to $7 $3 to $5 $1 to $3 $1 or less Quantity Demanded 0 1 2 3 4

Bert’s demand curve is shown in Figure 9.

Figure 9

b.

When the price of a bottle of water is $4, Bert buys two bottles of water. His consumer surplus is shown as area A in the figure. He values his first bottle of water at $7, but pays only $4 for it, so has consumer surplus of $3. He values his second bottle of water at $5, but pays only $4 for it, so has consumer surplus of $1. Thus Bert’s total consumer surplus is $3 + $1 = $4, which is the area of A in the figure.

c.

When the price of a bottle of water falls from $4 to $2, Bert buys three bottles of water, an increase of one. His consumer surplus consists of both areas A and B in the figure, an increase in the amount of area B. He gets consumer surplus of $5 from the first bottle ($7 value minus $2 price), $3 from the second bottle ($5 value minus $2 price), and $1 from the third bottle ($3 value minus $2 price), for a total consumer surplus of $9. Thus consumer surplus rises by $5 (which is the size of area B) when the price of a bottle of water falls from $4 to $2.

4、假设技术进步使生产电脑的成本降低了。

a．用供求图说明电脑市场上价格、数量、消费者剩余和生产者剩余会发生什么变动。

b．电脑和加法机是替代品。用供求图说明加法机市场上的价格、数量、消费者剩余和生产者剩余会

发生什么变动。电脑技术进步对加法机生产者而言是有幸还是不幸？

c．电脑和软件是互补品。用供求图说明软件市场上的价格、数量、消费者剩余和生产者剩余会发生什么变动。电脑技术进步对软件生产者而言是有幸还是不幸？

a.

The effect of falling production costs in the market for computers results in a shift to the right in the supply curve, as

shown in Figure 14. As a result, the equilibrium price of computers declines and the equilibrium quantity increases. The decline in the price of computers increases consumer surplus from area A to A + B + C + D, an increase in the amount B + C + D.

Figure 14

Prior to the shift in supply, producer surplus was areas B + E (the area above the supply curve and below the price). After the shift in supply, producer surplus is areas E + F + G. So producer surplus changes by the amount F + G – B, which may be positive or negative. The increase in quantity increases producer surplus, while the decline in the price reduces producer surplus. Since consumer surplus rises by B + C + D and producer surplus rises by F + G – B, total surplus rises by C + D + F + G.

Figure 15

b.

Since adding machines are substitutes for computers, the decline in the price of computers means that people substitute computers for adding machines, shifting the demand for adding machines to the left, as shown in Figure 15. The result is a decline in both the equilibrium price and equilibrium quantity of adding machines. Consumer surplus in the adding-machine market changes from area A + B to A + C, a net change of C – B. Producer surplus changes from area C + D + E to area E, a net loss of C + D. Adding machine producers are sad about technological advance in computers because their producer surplus declines.

c.

Since software and computers are complements, the decline in the price and increase in the quantity of computers means that the demand for software increases, shifting the demand for software to the right, as shown in Figure 16. The result is an increase in both the price and quantity of software. Consumer surplus in the software market changes from B + C to A + B, a net change of A – C. Producer surplus changes from E to C + D + E, an increase of C + D, so software producers should be happy about the technological progress in computers.

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