Question

 6. Short-run supply and long-run equilibrium

 Consider the competitive market for copper. Assume that, regardless of how many firms are in the industry, every firm in the Industry is identical and faces the marginal cost (MC), average total cost (ATC), and average variable cost (AVC) curves shown on the following graph.

 The following diagram shows the market demand for copper.

 Use the orange points (square symbol) to plot the initial short-run industry supply curve when there are 20 firms in the market. (Hint: You can disregard the portion of the supply curve that corresponds to prices where there is no output, since this is the industry supply curve.) Next, use the purple points (diamond symbol) to plot the short-run industry supply curve when there are 40 firms. Finally, use the green points (triangle symbol) to plot the short-run industry supply curve when there are 60 firms.

 If there were 60 firms in this market, the short-run equilibrium price of copper would be _______  per pound. At that price, firms in this Industry would _______ .

 Therefore, in the long run, firms would _______  the copper market.

 Because you know that competitive firms earn _______  economic profit in the long run, you know the long-run equilibrium price must be _______  per pound. From the graph, you can see that this means there will be _______  firms operating in the copper industry in long-run equilibrium.

Answer 1

Answer:

P = MC	Q	Q=20 firms	Q = 40 firms	Q=60 frims
16	12	240	480	720
40	15	300	600	900
52	16	320	640	960
64	17	340	680	1020
80	18	360	720	1080

If there were 60 firms in this market, the short-run equilibrium price of copper would be $ 40 per pound. At that price, firms in this industry would earn negative profit (ATC > P). Therefore, in the long run, firms would exit the copper market.

Because you know that competitive firms earn zero economic profit in the long run, you know the long-run equilibrium price must be $52 per pound. From the graph, you can see that this means there will be 20 firms operating in the copper industry in long-run equilibrium.