Q$3.$ A fluid $($viscosity$=1\mathrm{.}5$ g $c{m}^{-1}{s}^{-1},$ kinematic viscosity $=1\mathrm{.}75c{m}^2{s}^{-1})$ is flowing down an inclined wall with a mass flow rate of $250\frac{t}{h}.$ If the fluid thickness is $2$ cm for a wall width of $2\mathrm{.}1$ m $,$ what should be the mean velocity of this fluid and the angle with the vertical plane?

$(20$ points$)$