Exhibit 8.9 Marginal cost 5 P5 Average total cost da Dollars per unit 3 Average variable cost 2. 91 92 43 94 95 Quantity por poriod Refer to Exhibit 8.9, which shows a perfectly competitive firm's short-run output decisions. At price pa, the firm O a, is indifferent between producing and shutting down. b. earns short-run economic profit by producing at a specific output. O c. produces nothing. O d. produces at a specific output to earn a normal profit. O e. produces at a specific output to minimize its short-run loss