$5\_3$ When study a pressure$-$driven flow field in a rectangular flow chamber, the rectangular testing section is

designed with a dimension of $W$ wide, $H$ high, and $L$ long $($where$,LWH).$ If the pressure drop

measured from the two longitudinal end of the testing section is $p(e.g.,\frac{dp}{dx}=-\frac{p}{L}),$ it is proposed by

one of the researchers that the wall shear stress satisfies the following equation: ${}_w=\frac{p}{2(H+W)L}*HW.$

Please show the procedure by which the researcher has used to obtain this equation and discuss that if

the equation is correct or not.

Please derive it and not just explain it