6.31 A 220-V DC shunt motor has armature and field winding resistances of 0.15Ω and 110Ω, respectively. The motor draws a line current of 5A while running at 1,200 rpm on no load. When driving a load, the input to the motor is 12 kW. Calculate:
1. The speed of the motor
2. The developed torque
3. The efficiency of the motor at this load