\nIn perfect competition, a firm is a price taker, meaning the market price (P) is constant for the firm and equals its Marginal Revenue (MR) and Average Revenue (AR). A firm maximizes profit by producing at the output level where Marginal Cost (MC) equals Marginal Revenue (MR). Thus, the equilibrium condition is P = MR = MC.
\nLet’s evaluate the statements:
\nA) The market price must be greater or equal to average variable cost in the short run: Correct. A firm continues to produce in the short run only if the price is at least equal to the average variable cost (P \u2265 AVC). If P < AVC, the firm minimizes losses by shutting down.\nB) The market price must be equal to marginal cost: Correct. P = MC is the profit-maximizing (or loss-minimizing) condition for a firm in perfect competition.\nC) The market price must be equal to average cost in the long run: Correct. In the long run equilibrium of a perfectly competitive market, entry and exit of firms ensure that price equals the minimum average total cost (P = MC = ATC), resulting in zero economic profit for all firms.\nD) The marginal cost decreases at the equilibrium output: Incorrect. For the equilibrium at P=MC to be stable and represent profit maximization, the MC curve must be rising at the point of intersection with the MR (Price) line. If MC were decreasing at equilibrium, producing more would increase profit (or decrease loss) because the cost of the next unit would be less than the revenue it generates (P). Firms produce on the upward-sloping portion of their MC curve above the AVC curve.\n<\/section>\n