Kenny McCormick manages a 100-unit apartment building and knows from experience that all units will be occupied if rent is $900 per month. McCormick also knows that, on average, one additional unit will go unoccupied for each $10 increase in the monthly rental rate.

A. Estimate the apartment rental demand curve assuming that it is linear and that price is expressed as a function of output.

B. Calculate the revenue-maximizing apartment rental rate. How much are these maximum revenues?

C. If all costs are fixed, what is the profit-maximizing number of vacant apartments? Explain your answer.