Problem 3:
A 2-D force system acts on the frame, P_(1)=80N,P_(2)=100N,P_(3)=50N,m=200N-m, and
unknown forces Ax, Ay, Dy with a =0.2m. If the moment of all the forces and couple about A is
zero, determine the magnitude of the force Dy and direction. Use Mp=(+)/(-)Fd scalar form for 2D.