FIGURE $4\mathrm{.}8$ Force on a submerged plane area.

The tank shown in Fig. $4\mathrm{.}8$ contains a lubricating oil with a specific gravity of $0\mathrm{.}91.$ A rectangular v with the dimensions $B=4ft$ and $H=2ft$ is placed in the inclined wall of the tank centroid of the window is at a depth of $5ft$ from the surface of the oil. Calculate $($a$)$ the magnitude resultant force $F_R$ on the window and $($b$)$ the location of the center of pressure.