In a certain reservoir pump installation (Rao 2009), the first cost of the pipe is given by (100D + 50D2 ), where D is the diameter of the pipe in centimeters. The cost of the reservoir decreases with an increase in the quantity of fluid handled and is given by 20/Q, where Q is the rate at which the fluid is handled (m3 /s). The pumping cost is given by (300Q2 /D5). Find the optimal size of the pipe and the amount of fluid handled for minimum overall cost.