4-81. Two couples act on the frame. If d = 4 ft, determine the resultant couple moment. Compute the result by resolving each force into x and y components and (a) finding the moment of each couple (Eq. 413) and (b) summing the moments of all the force components about point B. 2 ft- - 3 ft- 50 lb 30 B 1 ft 30 50 Ib 80 lb 3 ft 80 lb Probs. 4-79/80/81