Given: A horizontal flat plate is sliding over a stationary flat plate at a velocity of $0\mathrm{.}4\frac{m}{s}.$ There is a $0\mathrm{.}25mm(0$:$00025m)$ layer

of oil between them. The surface area of contact is $3\mathrm{.}5m^2$ and the absolute viscosity of the oil is $0\mathrm{.}12N-\frac{s}{m^2}.$ Find: a$)$ the shear

stress, tau, $($in $\frac{N}{m^2})$ in the fluid between the two plates, and b$)$ the force $F($in N $)$ that must be applied to move the upper plate

at the given velocity. Assume the velocity profile between the two plates is linear $($Couette flow$).$