I like step by step solution typed up$.$ But I also like a simple way of doing it without a lot of steps.

The force $(kN)$ needed to hold the $2m$ wide hinged gate

in position is most nearly

$($a$)12\mathrm{.}5$

$($b$)8\mathrm{.}6$

$($c$)3\mathrm{.}5$

$($d$)5\mathrm{.}4$

Topic:

Forces on Submerged Surfaces