The profit-maximizing choice for a perfectly competitive firm will occur at the level of output where marginal revenue is equal to marginal cost—that is, where MR = MC. This occurs at Q = 80 in the figure.
Marginal revenue is the increase in revenue that results from the sale of one additional unit of output.
While marginal revenue can remain constant over a certain level of output, it follows from the law of diminishing returns and will eventually slow down as the output level increases.
To calculate marginal revenue, you take the total change in revenue and then divide that by the change in the number of units sold.
The marginal revenue formula is: marginal revenue = change in total revenue/change in output.
Learn more about marginal revenue here:
