$2\mathrm{.}8\mathrm{.}7($WP$)$ A piston having a cross$-$sectional area of $0\mathrm{.}07m^2$ is located

in a cylinder containing water, as shown in Fig. P$2\mathrm{.}8\mathrm{.}7.$ An open

U$-$tube manometer is connected to the cylinder as shown. For $h_1=$

$60$ mm and $h=100mm,$ what is the value of the applied force, $P,$

acting on the piston? The weight of the piston is negligible.

FIGURE P$2\mathrm{.}8\mathrm{.}7$