In a 60-HZ, 208 V (line-line, rms), 5-kW motor, R'r = 0.45Ω and X'tr = 0.83Ω. The rated torque is developed at the slip s = 0.04. Assuming that the motor is supplied with rated voltages and is delivering the rated torque, calculate the rotor power factor angle. What is Br/Bms?