A shaft 1.6 m long is 95 mm in diameter for the first 0.6 m of its length, 60 mm in diameter for the next 0.5 m of the length and 50 mm in diameter for the remaining length. The shaft carries two rotors at two ends, the first having a mass of 800 kg and 0.85 m radius of gyration located at the 95 mm diameter end and the second having a mass of 600 kg and 0.55 m radius of gyration located at the other end. Determine the location of the node and natural frequency of torsional vibration of the system. Take C = 80GN/m2.