A perfectly competitive firm faces a price of 10 and is currently producing a level of output at which marginal cost is equal to 10 on a rising portion of its short- run marginal cost curve. Its long- run marginal cost is equal to 12. Its short- run average variable cost is equal to 8. The minimum point on its long-run average cost curve is equal to 10. Is this firm earning an economic profit in the short run? Should it alter its output in the short run? In the long run, what should this firm do?