For a certain firm, the 100th unit of output that the firm produces has a marginal revenue of $7 and a marginal cost of $10. It follows that the Select one: a. production of the 100th unit of output increases the firm's profit by $3. b. production of the 100th unit of output increases the firm's average total cost by $7. c. firm's profit-maximizing level of output is less than 100 units. d. production of the101st unit of output must increase the firm's profit by more than $3.