A DC shunt motor rotating at 1560 RPM is supplied from a 240-V source. The line current supplied to the motor is equal to 27 A. The shunt field resistance of the motor is equal to 120 Ω and the armature resistance is equal to 0.6 Ω. Calculate the following:
(a) The armature current of the machine.
(b) The back-emf.
(c) The output mechanical power and the net torque developed by the motor if its mechanical losses are equal to 280 W.