Suppose the most you would be willing to pay to have a freshly washed car before going out on a date is $8.00. The smallest amount for which you would be willing to wash someone else's car is $5.50. You are going out this evening and your car is dirty. How much economic surplus would you receive from washing it

1. The most you would be willing to pay for having a freshly washed car before going out on a

date is $6. The smallest amount for which you would be willing to wash someone else's car is

$3.50. You are going out this evening, and your car is dirty. How much economic surplus

would you receive from washing it?

The economic surplus from washing your dirty car is the benefit you receive from doing so ($6)

minus your cost of doing the job ($3.50), or $2.50.

2. To earn extra money in the summer, you grow tomatoes and sell them at the farmers' market

for 30 cents per pound. By adding compost to your garden, you can increase your yield as

shown in the table below. If compost costs 50 cents per pound and your goal is to make as much

money as possible, how many pounds of compost should you add?

Pounds

of

compost

Pounds

of

tomatoes

Marginal

Cost

($)

Marginal

Benefit

(pounds)

Marginal

Benefit

($)

Net

Benefits

Marginal

Net

Benefits

0 100 0 --- 0 ---

1 120 0.50 20 6.00 5.50 5.50

2 125 0.50 5 1.50 6.50 1.00

3 128 0.50 3 0.90 6.90 0.40

4 130 0.50 2 0.60 7.00 0.10

5 131 0.50 1 0.30 6.80 - 0.20

6 131.5 0.50 0.5 0.15 6.45 - 0.35

The benefit of adding a pound of compost is the extra revenue you’ll get from the extra tomatoes

that result. The cost of adding a pound of compost is 50 cents. By adding the fourth pound of

compost you’ll get 2 extra pounds of tomatoes, or 60 cents in extra revenue, which more than

covers the 50-cent cost of the extra pound of compost. But adding the fifth pound of compost

gives only 1 extra pound of tomatoes, so the corresponding revenue increase (30 cents) is less than

the cost of the compost. You should add 4 pounds of compost and no more.

3. Residents of your city are charged a fixed weekly fee of $6 for garbage collection. They are

allowed to put out as many cans as they wish. The average household disposes of three cans of

garbage per week under this plan. Now suppose that your city changes to a "tag" system. Each

can of refuse to be collected must have a tag affixed to it. The tags cost $2 each and are not

reusable. What effect do you think the introduction of the tag system will have on the total

quantity of garbage collected in your city? Explain briefly.

In the first case, the cost is $6/week no matter how many cans you put out, so the cost of

disposing of an extra can of garbage is $0. Under the tag system, the cost of putting out an extra

can is $2, regardless of the number of the cans. Since the relevant costs are higher under the tag

system, we would expect this system to reduce the number of cans collected.

Explanation: