Two bevel gears A and B (having 60 teeth and 40 teeth, respectively) are rigidly mounted on two co-axial shafts X and Y as shown in Fig. A bevel gear C (having 50 teeth) meshes with A and B and rotates freely on one end of an arm. At the other end of the arm is welded a sleeve and the sleeve is riding freely loose on the axes of the shafts X and Y. If the shaft X rotates at 120 r.p.m. clockwise and the arm rotates at 120 r.p.m. anticlockwise, find the speed of shaft Y.