Pure water is running at $0\mathrm{.}05\frac{m}{s}$ inside a tube with an inside diameter of $3cm$ at $25C.$ The tube's inside wall is coated with

benzoic adid which is being dissolved with its diffusivity of $1\mathrm{.}245{10}^{-9}\frac{m^2}{s}.$ Assuming that the velocity profle is fully developed

and the pressure of benzoic acid on the tube surface is $0\mathrm{.}015$atm, calculate the total moles of benzoic acid diffused into water

flow for $1$ hour. The full length of the tube is $1$ meter. The physical properties of water at this condition are as follows: $p=996$

$k\frac{g}{m^2},=8\mathrm{.}71{10}^{-4}Pa-s.(30$ point$)$