In a perfectly competitive market, what condition describes the long-run equilibrium for firms in terms of marginal revenue and marginal cost?

In a perfectly competitive market, long-run equilibrium occurs when firms produce at a point where marginal revenue equals marginal cost. This means that the extra money a firm makes from selling one more unit of a product (marginal revenue) is exactly equal to the extra cost of producing that unit (marginal cost). At this point, firms are maximizing their profits because they are not missing out on potential earnings or wasting resources. For example, if a bakery can sell one more loaf of bread for $2 (marginal revenue) and it costs them $2 to make that loaf (marginal cost), they are in equilibrium. If these conditions hold true for all firms in the market, it leads to a stable situation where no firm has an incentive to change its production level.