Answer: "If a perfectly competitive firm is producing output at a point where marginal revenue is equal to marginal cost, then it should stick with that level of production in order to maximize profits".
Explanation: Companies in a market of perfect competition choose to produce at a point where their marginal income is equal to their marginal costs to maximize profits, because the marginal income is the change in total income for each additional amount sold, and the marginal cost is the cost of produce an additional unit of good.
Therefore, at this point the costs of producing one more unit do not exceed the benefits obtained by its sale.