The steel uniform shaft has four pulleys attached to it and frictionless bearings at its ends. The pulley at B is connected to a motor that is driving the system. The other three pulleys are consuming the power delivered by Pb . Pa = 20kW, Pb = 75kW, Pc = 30kW and Pd = 25kW and the shaft is rotating at 120rpm. Determine the diameter of the shaft if the allowable shear stress is 50MPa.