Under conditions of perfect competition, a firm's supply curve is determined by its?

In perfect competition, a firm's supply curve is determined by its marginal cost curve. The marginal cost curve represents the additional cost of producing one more unit of output. In a perfectly competitive market, firms are price-takers and cannot influence the market price. Therefore, the optimal output level for a firm is where its marginal cost equals the market price. As the market price changes, the optimal output level for the firm also changes. Thus, the firm's supply curve is the portion of its marginal cost curve that lies above the market price. Therefore, in perfect competition, the firm's supply curve is determined by its marginal cost curve.