复习题：

1. A consumer has income of $3,000. Wine costs $3 a glass, and cheese costs $6 a pound. Draw the consumer’s budget constraint. What is the slope of this budget
constraint?

答：斜率是-0.5

2. Draw a consumer’s indifference curves for wine and cheese. Describe and explain four properties of these indifference curves.

答： 高处的无差异曲线优于低处

     无差异曲线向下倾斜

     无差异曲线不相交

     无差异曲线向内弓起

3. Pick a point on an indifference curve for wine and cheese and show the marginal rate of substitution. What does the marginal rate of substitution tell us?

答：为了多得到一磅奶酪而愿意放弃的红酒杯数。

4. Show a consumer’s budget constraint and indifference curves for wine and cheese. Show the optimal consumption choice. If the price of wine is $3 a glass
and the price of cheese is $6 a pound, what is the marginal rate of substitution at this optimum?

答：消费无差异曲线和预算约束线相切点，是消费者的最优消费点。

    这时候的边际替代率就是预算约束线的斜率=6/3=2

5. A person who consumes wine and cheese gets a raise, so his income increases from $3,000 to $4,000. Show what happens if both wine and cheese are normal goods.
Now show what happens if cheese is an inferior good低档物品.

答：如果红酒和奶酪都是正常物品，则加薪后：

如果奶酪是低档物品

6. The price of cheese rises from $6 to $10 a pound, while the price of wine remains $3 a glass. For a consumer with a constant income of $3,000, show what happens to consumption of wine and cheese. Decompose the change into income and substitution effects.

答：

如图，奶酪的价格上升，导致横轴截距从500到300， 消费者预算约束线从BC1移动到BC2，最优选择点从A移动到B， 为了把这个变化分解为收入效应和替代效应，我们画出消费者约束线BC3，BC3 和BC2 平行，但是和最初的消费者无差异曲线相切。 从A点到C点的移动，代表替代效应。 因为奶酪变得更贵，消费者用红酒代替奶酪，导致从A移动到C。 从C移动到B，代表收入效应，奶酪涨价意味着收入降低。

7. Can an increase in the price of cheese possibly induce a consumer to buy more cheese? Explain.

答：如果奶酪是吉芬商品，那么奶酪的价格提高，会使消费者买更多的奶酪。在这种情况下，奶酪涨价的收入效应去导致人们买更多的低档商品。如果收入效应不敌替代效应，则人们会买更多奶酪。

应用题：

1. Jennifer divides her income between coffee and croissants (both of which are normal goods). An early frost in Brazil causes a large increase in the price of
coffee in the United States.
a. Show the effect of the frost on Jennifer’s budget constraint.

答：

b. Show the effect of the frost on Jennifer’s optimal consumption bundle assuming that the substitution effect outweighs the income effect for croissants.

答：如果替代效应大于收入效应，则如上图。

c. Show the effect of the frost on Jennifer’s optimal consumption bundle ssuming that the income effect outweighs the substitution effect for croissants.

答：

2. Compare the following two pairs of goods: Coke and Pepsi Skis and ski bindings
In which case do you expect the indifference curves to be fairly straight, and in which case do you expect the indifference curves to be very bowed? In which case will the consumer respond more to a change in the relative price of the two goods?

答：可口可乐和百事可乐之间的无差异曲线是直线，它们是完美的替代品。滑雪板和滑雪鞋带之间的无差异曲线是很大的弓形，因为他们是互补品。可口可乐或百事可乐之间的价格变动会使消费者反应很大，甚至可能完全转向另外一种产品。 

3. Mario consumes only cheese and crackers.
a. Could cheese and crackers both be inferior goods for Mario? Explain.

答：不可能。因为如果他的收入增加了，他肯定要多消费两种产品中的某种。

b. Suppose that cheese is a normal good for Mario whereas crackers are an  inferior good. If the price of cheese falls, what happens to Mario’s consumption
of crackers? What happens to his consumption of cheese? Explain.

答：如果奶酪是正常商品，而饼干是低档产品。奶酪价格下降，替代效应使他多消费奶酪少消费饼干。收入效应将使他多消费奶酪少消费饼干。所以，总体效果是多消费奶酪少消费饼干。

4. Jim buys only milk and cookies.
a. In 2001, Jim earns $100, milk costs $2 per quart, and cookies cost $4 per dozen. Draw Jim’s budget constraint.

答：

b. Now suppose that all prices increase by 10 percent in 2002 and that Jim’s salary increases by 10 percent as well. Draw Jim’s new budget constraint. How
would Jim’s optimal combination of milk and cookies in 2002 compare to his optimal combination in 2001?

答：不用变。

5. Consider your decision about how many hours to work.
a. Draw your budget constraint assuming that you pay no taxes on your income. On the same diagram, draw another budget constraint assuming that you pay a 15 percent tax.

答：

b. Show how the tax might lead to more hours of work, fewer hours, or the same number of hours. Explain.

 答：

如果收入效应超过替代效应，则导致工作时间加长。如上图。

如果替代效应超过了收入效应，则导致工作时间减少。如上图。

如果替代效应和收入效应相等，则工作时间不变。

6. Sarah is awake for 100 hours per week. Using one diagram, show Sarah’s budget constraints if she earns $6 per hour, $8 per hour, and $10 per hour. Now draw
indifference curves such that Sarah’s labor supply curve is upward sloping when the wage is between $6 and $8 per hour, and backward sloping when the wage is
between $8 and $10 per hour.

答：