For a certain firm, the 100th unit of output that the firm produces has a marginal revenue of $10 and a marginal cost of $7. It follows that the :O production of the 100th unit of output increases the firm's profit by $3.O production of the 100th unit of output increases the firm's average total cost by $7.O firm's profit-maximizing level of output is less than 100 units. O production of the 99th unit of output must increase the firm