A 240 V,dc separately excited motor drives a constant-torque load at aspeed of 1500 rpm. The armature andfield resistance are 2 ? and 210? respectively. The motor draws a current of 20 A at givenload. Armature resistance method of speed control is employed tocontrol the speed of the motor. Calculate (a)the resistance that should be added to the armature circuit toreduce the speed by 40% and (b) the resistance that must be added to the armature circuit so that motor operatesat holding condition.