Fill in the blanks to make the following statements correct.
a. The demand curve faced by a single firm in a perfectly competitive market is _______.
b. The demand curve faced by a single firm in a perfectly competitive industry coincides with the firm's _______ curve and its _______ curve.
c. Total revenue is calculated by multiplying _______ and _______. Average revenue is calculated by dividing _______ by _______. Marginal revenue is calculated _______ by _______.
d. A firm's loss when it produces no output is equal to its _______.