A large rotor, weight $244$ kg $,$ has its radius of gyration $0\mathrm{.}8$ m $.$ The rotor is bolted between two

different diameter shafts. The first shaft has $932$ mm long and $77$ mm diameter and the second

shaft has $450$ mm long and $67$ mm diameter. The other ends of the shafts are rigidly fixed in

position. Assume the modulus of rigidity of the shaft is $81$ GPa $.$ Calculate the torsional frequency

of the system $(Hz)?$