An inclined rectangular gate $($width of $0\mathrm{.}5$ m into the page, and inclined length of $0\mathrm{.}6$ m $)$

has an inclination angle of $45$ and its top edge $12$ m below the water surface $($see the

schematic$).$ Calculate the minimum force $P($perpendicular to the gate as shown in the

schematic$)$ needed to open the gate.