A square gate $(4m$ by $4m)$ is located on the $45$ slanted face of a dam $($see figure below$).$ The

top edge of the gate lies $8m$ below the water surface. FIND: $($a$)$ the force of the water on the gate

$($FR$),$ and $($b$)$ the point through which it acts $(yR,$ center of pressure$)$