An ‘SS’ tube is inserted into an ‘Al' tube.They are permently fixed at one end .The other end is attached to a rigid plate .A torque "T" is applied to the rigid plate .A torque "T" is applied to the rigid plate .The circumference of the 'Al' tube at dia 'D' at the plate end with respect to the fixed end rotates by a distance ....mm due to the TORQUE 'T'.The polar MOI & rigidity modulus of Al & ss are $$J_{Al},G_{Al}$$ and $$J_{ss},G_{ss}$$ respectively