A 10kW, 400 V, 3-phase, 6-pole, 50 Hz slip ring induction motor has a maximum torque

A 10kW, 400 V, 3-phase, 6-pole, 50 Hz slip ring induction motor has a maximum torque equal to twice the full load torque at a slip of 20%, with slip rings short circuited. Neglecting stator resistance and rotational losses, determine the slip at full load, starting torque and torque developed at a slip of 0.25. If the rotor circuit resistance is increased to four times by connecting resistance in series with each rotor slip ring, determine, (a) the slip at maximum torque, (b) the slip at which the motor will develop the same full load torque (c) the starting torque.