Find the rate of change of total revenue, cost, and profit with respect to time. Assume that R(x) and C(x) are in dollars. R(x) = 45x - 0.5x , C(x) =3x + 15, when x = 30 and dx / dt = 25 units per day The rate of change of total revenue is $ per day. The rate of change of total cost is $ per day. The rate of change of total profit is $ per day