经济学原理曼昆课后答案chapter13

Problems and Applicat ions

1. a. opportunity cost; b. average total cost; c. fixed cost; d. variable cost; e. total cost;f. marginal cost.

2. a. The opportunity cost of something is what must be forgone to acquire it.b. The opportunity cost of running the hardware store is $550,000, consisting of$500,000 to rent the store and buy the stock and a $50,000 opportunity cost,since your aunt would quit her job as an accountant to run the store. Sincethe total opportunity cost of $550,000 exceeds revenue of $510,000, your auntshouldn't open the store, as her profit would be negative she would losemoney.

3. a. Since you'd have to pay for room and board whether you went to college or not,that portion of your college payment is not an opportunity cost.b. The explicit opportunity cost is the cost of tuition.

c. An implicit opportunity cost is the cost of your time. You could work at a jobfor pay rather than attend college. The wages you give up represent anopportunity cost of attending college.

4. a. The following table shows the marginal product of each hour spent fishing:

b. Figure 13-7 graphs the fisherman's production function. The productionfunction becomes flatter as the number of hours spent fishing increases,illustrating diminishing marginal product.

Figure 13-7

c. The table shows the fixed cost, variable cost, and total cost of fishing. Figure13-8 shows the fisherman's total-cost curve. It slopes up because catchingadditional fish takes additional time. The curve is convex because there arediminishing returns to fishing time each additional hour spent fishing yieldsfewer additional fish.

5. Here’s the table of costs:

a. See table for marginal product. Marginal product rises at first, then declinesbecause of diminishing marginal product.b. See table for total cost.

c. See table for average total cost. Average total cost is U-shaped. When

quantity is low, average total cost declines as quantity rises; when quantity ishigh, average total cost rises as quantity rises.

d. See table for marginal cost. Marginal cost is also U-shaped.

e. When marginal product is rising, marginal cost is falling, and vice versa.f. When marginal cost is less than average total cost, average total cost is falling;when marginal cost is greater than average total cost, average total cost isrising.

6. Fixed costs include the cost of owning or renting a car to deliver the bagels and the

cost of advertising; they're fixed costs because they don't vary with output. Variable costs include the cost of the bagels and gas for the car, since

those costs will increase as output increases.

7. a. The fixed cost is 300, since fixed cost equals total cost minus variable cost.b.

Marginal cost equals the change in total cost or the change in variable cost.That's because total cost equals variable cost plus fixed cost and fixed costdoesn't change as the quantity changes. So as quantity increases, theincrease in total cost equals the increase in variable cost and both are equal tomarginal cost.

8. a. The fixed cost of setting up the lemonade stand is $200. The variable costper cup is 50 cents.

Figure 13-9

b. The following table shows total cost, average total cost, and marginal cost.These are plotted in Figure 13-9.

9. The following table illustrates average fixed cost (AFC), average variable cost (AVC),and average total cost (ATC) for each quantity. The efficient scale is 4 houses permonth, since that minimizes average total cost.

10. a. The following table shows average variable cost (AVC), average total cost (ATC),and marginal cost (MC) for each quantity.

b. Figure 13-10 graphs the three curves. The margi nal cost curve is below theaverage total cost curve when output is less than 4, as average total cost isdeclining. The marginal cost curve is above the average total cost curvewhen output is above 4, as average total cost is rising. The marginal costcurve is always above the average variable cost curve, and average variablecost is always increasing.

Figure 13-10

11. The following table shows quantity (Q), total cost (TC), and average total cost (ATC)for the three firms:

Firm A has economies of scale since average total cost declines as output increases.

Firm B has diseconomies of scale since average total cost rises as output rises. Firm C has economies of scale for output from 1 to 3, thendiseconomies of scale for greater levels of output.