Use the scalar method to find the moment about point A of the three forces acting on the b in a counterclockwise direction.
F = 375 lb
F = 500 lb
8 ft
= 160 lb
O M4 = -375 x 8 - 500 x 14 - 160 x cos 30 x 19 + 160 x sin 30 x 0.5 lb.ft
O Ma = -375 x 8 - 500 x 14 - 160 x sin 30 x 19 + 160 x cos 30 x 0.5 lb.ft
O M4 = -375 x 8 - 500 x 3 x 14 - 160 x cos 30 x 19 + 160 x sin 30 x 0.5 lb.ft
O Ma = -375 x 8 - 500 x 14 - 160 x cos 30 x 19 lb.ft