The steel axle of a large winch on an ocean liner is subjected to a torque of

Question:

The steel axle of a large winch on an ocean liner is subjected to a torque of 1.65 kN . m (see figure). What is the minimum required diameter dmin if the allowable shear stress is 48 MPa and the allowable rate of twist is 0.75°/m? (Assume that the shear modulus of elasticity is 80 GPa.)