Pressure drop equation in a fully developed laminar flow in pipe - GATE ME '06

The velocity profile in fully developed laminar flow in a pipe of diameter D is given by u=uo(1− 4r^2/D^2), where r is the radial distance from the center. If the viscosity of the fluid is μ, the pressure drop across a length L of the pipe is _________ A. μ*uo*L /D^2 B. 4*μ*uo*L /D^2 C. 8*μ*uo*L /D^2 D. 16*μ*uo*L /D^2