Could you please solve it without integrating?

Figure $1$ shows a cross section of a submerged tunnel used by automobiles to travel under

a river. Find the magnitude and location of the resultant hydrostatic force on the semi$-$

circular roof of the tunnel. Assume the length $($dimension perpendicular to the screen$)$ of

the tunnel is b $($adopted from Muson et al$.$ P$2\mathrm{.}115)$

figure $1$