Because marginal revenue equals price for a perfectly competitive firm, the profit-maximizing rule MR = MC can also be written as a recommendation to produce where which condition holds?

1. Marginal revenue equals price for a price-taking firm, so wherever the rule says MR, price can be substituted instead. 2. Substituting price for marginal revenue turns MR = MC into P = MC. 3. P = AC describes the separate zero-profit condition, not the general profit-maximizing rule. 4. P = AVC describes the shutdown condition, a different rule entirely from the profit-maximizing output choice. _Source: OpenStax Principles of Microeconomics for AP Courses (CC BY 4.0), Ch 8 "Perfect Competition", section 8.2 | How Perfectly Competitive Firms Make Output Decisions_