Four masses A,B,C and D carried by a rotating shaft are at radius of rotation 100mm, 140mm, 210mm
and 100mm respectively. The planes in which the masses revolve are spaced 600mm apart and the masses
of B, C and D are 10kg, 10kg, and 12kg respectively. Find the required mass A and the relative angular
positions of the four masses so that shaft is in complete balance.