In a perfectly competitive market, the total revenue for a firm is the product of price and quantity. Meanwhile the average revenue is calculated by dividing total revenue with output quantity. And then the Marginal revenue is calculated by dividing the change in total revenue by change in quantity. Profit is maximized when Marginal revenue equals Marginal cost.
Therefore the answer to this is:
marginal revenue equals “average revenue, the price, and marginal cost for all levels of output”