$($write it on a paper$)$

$4.$W$.$ Water at $30C$ flows through a horizontal pipe $(1$ inch inside diameter$),$ in which the pressure drop is to be limited to $0\mathrm{.}015l{b}_{f}f{t}^{-2}$ per foot of length. This low pressure per foot is imposed by the excessively long line involved. Calculate the velocities $(ft{s}^{-1}),$ and the velocity distribution $U_z$ as a function of $r.$