Consider the gate shown in Fig.P2.8.13. The gate is massless and has a width b (perpendicular to the paper). The hydrostatic pressure on the vertical side creates a counterclockwise moment about the hinge, and the hydrostatic pressure on the horizontal side (or bottom) creates a clockwise moment about the hinge.Show that the net clockwise moment is \Sigma u=\rho_{w} g h b\left(\frac{\ell^{2}}{2}-\frac{h^{2}}{6}\right)