Two steel bars each of diameter 10mm are coaxially friction welded end to end at an axial pressure of 200MPa and rotational speed of 400rpm. The coefficent of friction between the mating faces of the rotating bars is 0.50. the torque is assumed to act at the 3/4th radius of the rotating bar. The power (in kW) consumed at the interface of the welding is
(a) 12.33 (b) 16.44 (c) 18.50 (d) 24.66