A dc motor has coils with a resistance of 16 and is connected to an emf

Question:

A dc motor has coils with a resistance of 16 Ω and is connected to an emf of 120.0 V. When the motor operates at full speed, the back emf is 72 V.
(a) What is the current in the motor when it first starts up?
(b) What is the current when the motor is at full speed?
(c) If the current is 4.0 A with the motor operating at less than full speed, what is the back emf at that time?