4. Suppose a company can sell 2500 units of a product every month when the price is $3.4 per unit, and the sales will reduce to 2000 units every month if the price is increased to $3.6 per unit. Let p be the price, and let q be the quantity that can be sold every month with price p. Suppose the demand function p = D(q) is linear, and the cost function is C(q) = 2.4q - 0.0015q2 + 1000. (a) Find the profit function P(q). (b) For which values of q does this company earn money