Answer:
The correct answer is marginal revenue equals marginal cost.
Explanation:
A monopoly is a form of market where there is only a single firm in the market. There is a restriction on the entry and exit of the firms. A monopoly firm is a price maker. It faces a downward-sloping demand curve. It can earn positive economic profits in both the long runs as well as the short run.
A monopoly firm maximizes its profit at the point where the marginal revenue earned is equal to marginal cost incurred in the production process.