(a) Let p be the price for one single unit, and let d(p) be the number of occupied units as the function of price. The condition says that d(250) = 0.9*30 = 27 units, and d(p) = 27 -. (1) Formula (1) is the answer to question (a). (b) Total revenue is the product of the number occupied units by the price per unit R(p) = d(p)*p = [ 27 - ]*p. (2) Formula (2) is the answer to question (b). You can simplify and transform this formula by any of equivalent ways.