$(1)$ As shown in the figure below, the total water pressure acting on the Tainter Gate with a width $($b$)$ of $10$m and

Find the point of action. The angle of inclination is $30\backslash$deg and r $=10$ m$.[1\mathrm{.}5$ points$]$

$($Water unit weight: $1$ tonf$/$m$3)$