Three rotors A, B and C having moments of inertia of 2000, 6000 and 3000 kg-m^2 respectively are carried on a uniform shaft of .35 m diameter. the length of the shaft between the rotors A and B is 6m and that between B and C is 32 m. Find the natural frequency of torsional vibration. the modulus of rigidity for the shaft material is 80 Gn/m^2.