Assume that for a certain product, its price function of demanding is p(x) = 25 - 0.03 x, where x is the quantity of the products. The total cost is C(x) = 1500 + 10x. What is the maximal profit and at what x it can he attained? (Hint, the total profit is given by P(x) = xp(x) - C(x).)