In the short run, there are 500 identical firms in a competitive market. The firms do not use any resources that are available in limited quantities, and each of them has the following cost structure: Output Total Cost 0 $0 1 $10 2 $12 3 $15 4 $24 5 $40 The long-run supply curve for this market is a. positively sloped. b. horizontally at a price of $3.33. c. horizontal at a price of $7. d. horizontal at a price of $5.