Suppose that a firm operating in perfectly competitive market sells 300 units of output at a price of $3 each. Which of the following statements is correct? (i) Marginal revenue equals $3. (ii) Average revenue equals $3. (iii) Total revenue equals $900. a. (i) only b. (iii) only c. (i) and (ii) only d. (i), (ii), and (iii)