Answer:
2. marginal revenue.
Explanation:
Marginal cost is the extra expense incurred as a result of or producing or selling an additional unit. For a profit-maximizing firm, marginal cost is important as it indicates the point at which production should stop.
Marginal revenue is the income generated by the sale of an extra unit. If the marginal revenue is greater than the marginal cost, a firm will make profits if it produces and sells an extra unit.
A profit-maximizing firm should continue production until the marginal cost equal to marginal revenue. The cost associated with producing the last item should match the income from that item. Further production will result in a loss.