A vehicle is driven by an electric motor through a two-stage compound gear train: N_{1} = 18 (motor pinion), N_{2} = 72, N_{3} = 20 (on the shaft of N_{2}), N_{4} = 80. Each stage has an efficiency of 95 %. The output shaft (N_{4}) must supply 150 N·m at 150 rpm. Find (a) the motor speed in rpm and (b) the motor torque in N·m.