If there is a positive level of output at which a firm's profit is maximised in the short run, that condition must not hold at that output level.

Price = Short run Average Cost.

The correct answer is Option (3) → Price = Short run Average Cost.

If a firm’s profit is maximised at a positive level of output in the short run, then:

• Price = Short run Marginal Cost must hold — this is the profit-maximising condition under perfect competition.

• Short run Marginal Cost is non-decreasing at the profit-maximising level — this ensures we are at a minimum point or rising cost.

• Price ≥ Average Variable Cost — this condition ensures the firm continues to produce in the short run and does not shut down.

However, Price = Short run Average Cost does not have to hold when profit is maximised. In fact, if P = SAC, the firm earns zero economic profit. Therefore, this condition need not hold at the profit-maximising level — making it the correct answer.