Figure9-3Alex’s Optimal Quantity of Years of Schooling The optimal quantity is the quantity that generates the highest possible total profit. It is the largest quantity at which marginal benefit is greater than or equal to marginal cost. Equivalently, it is the quantity at which the marginal benefit and marginal cost curves intersect. Here, they intersect at 3 additional years of schooling. The table confirms that 3 is indeed the optimal quantity: it leads to the maximum total profit of $410 000.