If Profit Maximization in Perfect Competition is to Marginal Revenue as Long-Run Equilibrium is to what?

In perfect competition, profit maximization occurs when a firm produces at a level where its marginal cost equals marginal revenue. This means that the additional revenue gained from selling one more unit is exactly equal to the cost of producing that unit. In the long run, firms in perfect competition reach a state called long-run equilibrium, where the price equals both marginal cost and average total cost. This ensures that firms make zero economic profit, which is a normal return on investment. For example, if a bakery sells bread at a price that covers its costs but does not allow for extra profit, it is in long-run equilibrium, balancing supply and demand.