3.(20%)A company makes two substitute products whose demand functions are x1 = 200(p2 - p1), x2 = 500 + l00p1 - 180p2, where p1 and p2 are the prices per unit and x1 and x2 are the numbers of units sold. The cost of producing the two products are $ 0.5 and $ 0.75 per unit.
(a)Find the cost, revenue and profit functions.