Profit-maximizing quantity is found where

• A. MR = MC
• B. Price equals marginal cost
• C. Total revenue equals total cost
• D. ATC equals price

Answer: (A)

Profit-maximizing output comes from balancing the extra revenue you get from selling one more unit with the extra cost of producing that unit. This balance occurs when marginal revenue equals marginal cost.

If the additional revenue from one more unit, MR, is greater than the additional cost, MC, producing one more unit raises profit, so you should keep increasing output. If MR is less than MC, producing another unit would reduce profit, so you should cut back. The point where they are equal is the best tradeoff, giving the highest possible profit.

Why the other ideas don’t capture the maximization focus: total revenue equaling total cost would give zero profit, which is not about maximizing how much profit you earn. The idea that price equals marginal cost is a related condition in some models (like perfect competition) where MR equals price, but the general profit-maximizing rule is MR = MC. The condition ATC equals price describes zero profit in a specific long-run equilibrium, not the profit-maximizing level of output.