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) = 55x - 0.5x ^ 2, C(x) = 6x + 5 when x = 40 and dx/dt (x) = 15 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