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1、SOLUTIONS TO TEXT PROBLEMS:Quick Quizzes1.When a competitive firm doubles the amount it sells, the price remains the same, so its total revenue doubles.2.The price faced by a profit-maximizing firm is equal to its marginal cost because if price were above marginal cost, the firm could increase profi
2、ts by increasing output, while if price were below marginal cost, the firm could increase profits by decreasing output.A profit-maximizing firm decides to shut down in the short run when price is less than average variable cost. In the long run, a firm will exit a market when price is less than aver
3、age total cost.3.In the long run, with free entry and exit, the price in the market is equal to both a firms marginal cost and its average total cost, as Figure 1 shows. The firm chooses its quantity so that marginal cost equals price; doing so ensures that the firm is maximizing its profit. In the
4、long run, entry into and exit from the industry drive the price of the good to the minimum point on the average-total-cost curve.Figure 1Questions for Review1.A competitive firm is a firm in a market in which: (1) there are many buyers and many sellers in the market; (2) the goods offered by the var
5、ious sellers are largely the same; and (3) usually firms can freely enter or exit the market.2.Figure 2 shows the cost curves for a typical firm. For a given price (such as P*), the level of output that maximizes profit is the output where marginal cost equals price (Q*), as long as price is greater
6、 than average variable cost at that point (in the short run), or greater than average total cost (in the long run).Figure 23.A firm will shut down temporarily if the revenue it would get from producing is less than the variable costs of production. This occurs if price is less than average variable
7、cost.4.A firm will exit a market if the revenue it would get if it stayed in business is less than its total cost. This occurs if price is less than average total cost.5.A firm's price equals marginal cost in both the short run and the long run. In both the short run and the long run, price equa
8、ls marginal revenue. The firm should increase output as long as marginal revenue exceeds marginal cost, and reduce output if marginal revenue is less than marginal cost. Profits are maximized when marginal revenue equals marginal cost.6.The firm's price equals the minimum of average total cost o
9、nly in the long run. In the short run, price may be greater than average total cost, in which case the firm is making profits, or price may be less than average total cost, in which case the firm is making losses. But the situation is different in the long run. If firms are making profits, other fir
10、ms will enter the industry, which will lower the price of the good. If firms are making losses, they will exit the industry, which will raise the price of the good. Entry or exit continues until firms are making neither profits nor losses. At that point, price equals average total cost.7.Market supp
11、ly curves are typically more elastic in the long run than in the short run. In a competitive market, since entry or exit occurs until price equals the minimum of average total cost, the supply curve is perfectly elastic in the long run.Problems and Applications1.A competitive market is one in which:
12、 (1) there are many buyers and many sellers in the market; (2) the goods offered by the various sellers are largely the same; and (3) usually firms can freely enter or exit the market. Of these goods, bottled water is probably the closest to a competitive market. Tap water is a natural monopoly beca
13、use there's only one seller. Cola and beer are not perfectly competitive because every brand is slightly different.2.Since a new customer is offering to pay $300 for one dose, marginal revenue between 200 and 201 doses is $300. So we must find out if marginal cost is greater than or less than $3
14、00. To do this, calculate total cost for 200 doses and 201 doses, and calculate the increase in total cost. Multiplying quantity by average total cost, we find that total cost rises from $40,000 to $40,401, so marginal cost is $401. So your roommate should not make the additional dose.3.a.Rememberin
15、g that price equals marginal cost when firms are maximizing profit, we know the marginal cost must be 30 cents, since that is the price.b.The industry is not in long-run equilibrium since price exceeds average total cost.4.Once you have ordered the dinner, its cost is sunk, so it does not represent
16、an opportunity cost. As a result, the cost of the dinner should not influence your decision about stuffing yourself.5.Since Bobs average total cost is $280/10 = $28, which is greater than the price, he will exit the industry in the long run. Since fixed cost is $30, average variable cost is ($280 -
17、$30)/10 = $25, which is less than price, so Bob wont shut down in the short run.6.Heres the table showing costs, revenues, and profits:QuantityTotal CostMarginal CostTotal RevenueMarginal RevenueProfit0 $ 8- $ 0-$ -819 $ 1 8 $ 8 -12101168 6311124813413232819519640821627848821737 1056819a.The firm sh
18、ould produce 5 or 6 units to maximize profit.b.Marginal revenue and marginal cost are graphed in Figure 3. The curves cross at a quantity between 5 and 6 units, yielding the same answer as in part (a).c.This industry is competitive since marginal revenue is the same for each quantity. The industry i
19、s not in long-run equilibrium, since profit is positive.Figure 37.a.Figure 4 shows the short-run effect of declining demand for beef. The shift of the industry demand curve from D1 to D2 reduces the quantity from Q1 to Q2 and reduces the price from P1 to P2. This affects the firm, reducing its quant
20、ity from q1 to q2. Before the decline in the price, the firm was making zero profits; afterwards, profits are negative, as average total cost exceeds price.Figure 4b.Figure 5 shows the long-run effect of declining demand for beef. Since firms were losing money in the short run, some firms leave the
21、industry. This shifts the supply curve from S1 to S3. The shift of the supply curve is just enough to increase the price back to its original level, P1. As a result, industry output falls still further, to Q3. For firms that remain in the industry, the rise in the price to P1 returns them to their o
22、riginal situation, producing quantity q1 and earning zero profits.Figure 58.Figure 6 shows that although high prices cause an industry to expand, entry into the industry eventually returns prices to the point of minimum average total cost. In the figure, the industry is originally in long-run equili
23、brium. The industry produces output Q1, where supply curve S1 intersects demand curve D1, and the price is P1. At this point the typical firm produces output q1. Since price equals average total cost at that point, the firm makes zero economic profit.Now suppose an increase in demand occurs, with th
24、e demand curve shifting to D2. This causes "high prices" in the industry, as the price rises to P2. It also causes the industry to increase output to Q2. With the higher price, the typical firm increases its output from q1 to q2, and now makes positive profits, since price exceeds average
25、total cost.However, the positive profits that firms earn encourage other firms to enter the industry. Their entry, "an expansion in an industry," leads the supply curve to shift to S3. The new equilibrium reduces the price back to P1, "bringing an end to high prices and manufacturers&
26、#39; prosperity," since now firms produce q1 and earn zero profit again. The only long-lasting effect is that industry output is Q3, a higher level than originally.Figure 69.a.Figure 7 shows the typical firm in the industry, with average total cost ATC1, marginal cost MC1, and price P1.b.The ne
27、w process reduces Hi-Techs marginal cost to MC2 and its average total cost to ATC2, but the price remains at P1 since other firms cannot use the new process. Thus Hi-Tech earns positive profits.c.When the patent expires and other firms are free to use the technology, all firms average-total-cost cur
28、ves decline to ATC2, so the market price falls to P3 and firms earn no profits.Figure 710.The rise in the price of petroleum increases production costs for individual firms and thus shifts the industry supply curve up, as shown in Figure 8. The typical firm's initial marginal-cost curve is MC1 a
29、nd its average-total-cost curve is ATC1. In the initial equilibrium, the industry supply curve, S1, intersects the demand curve at price P1, which is equal to the minimum average total cost of the typical firm. Thus the typical firm earns no economic profit.The increase in the price of oil shifts th
30、e typical firm's cost curves up to MC2 and ATC2, and shifts the industry supply curve up to S2. The equilibrium price rises from P1 to P2, but the price does not increase by as much as the increase in marginal cost for the firm. As a result, price is less than average total cost for the firm, so
31、 profits are negative.In the long run, the negative profits lead some firms to exit the industry. As they do so, the industry-supply curve shifts to the left. This continues until the price rises to equal the minimum point on the firm's average-total-cost curve. The long-run equilibrium occurs w
32、ith supply curve S3, equilibrium price P3, industry output Q3, and firm's output q3. Thus, in the long run, profits are zero again and there are fewer firms in the industry.Figure 811.a.Figure 9 illustrates the situation in the U.S. textile industry. With no international trade, the market is in
33、 long-run equilibrium. Supply intersects demand at quantity Q1 and price $30, with a typical firm producing output q1.Figure 9b.The effect of imports at $25 is that the market supply curve follows the old supply curve up to a price of $25, then becomes horizontal at that price. As a result, demand e
34、xceeds domestic supply, so the country imports textiles from other countries. The typical domestic firm now reduces its output from q1 to q2, incurring losses, since the large fixed costs imply that average total cost will be much higher than the price.c.In the long run, domestic firms will be unabl
35、e to compete with foreign firms because their costs are too high. All the domestic firms will exit the industry and other countries will supply enough to satisfy the entire domestic demand.12.a.Figure 10 shows the current equilibrium in the market for pretzels. The supply curve, S1, intersects the d
36、emand curve at price P1. Each stand produces quantity q1 of pretzels, so the total number of pretzels produced is 1,000 x q1. Stands earn zero profit, since price equals average total cost.b.If the city government restricts the number of pretzel stands to 800, the industry-supply curve shifts to S2.
37、 The market price rises to P2, and individual firms produce output q2. Industry output is now 800 x q2. Now the price exceeds average total cost, so each firm is making a positive profit. Without restrictions on the market, this would induce other firms to enter the market, but they cannot, since th
38、e government has limited the number of licenses.c.The city could charge a license fee for the licenses. Since it is a lump-sum fee for the license, not based on the quantity of sales, such a tax has no effect on marginal cost, so won't affect the firm's output. It will, however, reduce the f
39、irm's profits. As long as the firm is left with a zero or positive profit, it will continue to operate. So the license fee that brings the most money to the city is to charge each firm the amount (P2 - ATC2)q2, the amount of the firm's profit.Figure 1013.a.Figure 11 illustrates the gold mark
40、et (industry) and a representative gold mine (firm). The demand curve, D1, intersects the supply curve at industry quantity Q1 and price P1. Since the industry is in long-run equilibrium, the price equals the minimum point on the representative firm's average total cost curve, so the firm produc
41、es output q1 and makes zero profit.b.The increase in jewelry demand leads to an increase in the demand for gold, shifting the demand curve to D2. In the short run, the price rises to P2, industry output rises to Q2, and the representative firm's output rises to q2. Since price now exceeds averag
42、e total cost, the representative firm now earns positive profits.c.Since gold mines are earning positive economic profits, over time other firms will enter the industry. This will shift the supply curve to the right, reducing the price below P2. But it's unlikely that the price will fall all the
43、 way back to P1, since gold is in short supply. Costs for new firms are likely to be higher than for older firms, since they'll have to discover new gold sources. So it's likely that the long-run supply curve in the gold industry is upward sloping. That means the long-run equilibrium price w
44、ill be higher than it was initially.Figure 1114.a.Figure 12 shows cost curves for a California refiner and a non-California refiner. Since the California refiner has access to lower-cost oil, its costs are lower.Figure 12b.In long-run equilibrium, the price is determined by the costs of non-Californ
45、ia refiners, since California refiners cannot supply the entire market. The market price will equal the minimum average total cost of the other refiners; they will thus earn zero profits. Since California refiners have lower costs, they will earn positive profits, equal to (P* - ATCC) x QC.c.Yes, there is a subsidy to California refiners that is not passed on to consumers. The subsidy accounts for the long-run profits of the California refiners. It arises simply because the oil cannot be exported.271 / 9文档可自由编辑打印