Fig. P$3\mathrm{.}114$ and P$3\mathrm{.}115$

$3\mathrm{.}115$ A couple M and the three forces shown are applied to an angle bracket. Find the moment of the couple if the line of action of the

resultant of the force system is to pass through $($a$)$ point $A,($b$)$ point $B,($c$)$ point $C.$