A 240-V, 60-Hz, two-pole universal motor operates at a speed of 12,000 rev/min on full load and draws a current of 6.5 A at 0.94 power factor lagging. The series field-winding impedance is 4.55 + j3.2 ohms, and the armature circuit impedance is 6.15 + j9.4 ohms. Find
a. The back emf of the motor.
b. The mechanical power developed by the motor.
c. The power output if the rotational loss is 65 W.
d. The efficiency of the motor.