Answer: Option (b) is correct.
Step-by-step explanation:
Correct option: price equals marginal cost.
In a perfectly competitive market and a profit maximizing firm, the profit maximizing level of output is at the point where marginal cost is equal to the price of the product.
In the perfectly competitive market, there are large number of buyers and sellers and price of the product is determined by the market forces.
At, P = MC, firms earns zero economic profit.