A 15 kW, 230 V dc shunt motor has armature circuit, resistance of 0.4 Ω and field circuit resistance of 230 Ω.  At no load and rated voltage, the motor runs at 1440 rpm and the line current drawn by the motor is 5 A. At full load, the motor draws a line current of 70 A. Neglect armature reaction. The full load speed of the motor in rpm