The electric motor exerts a torque of 800 N·m on the steel shaft ABCD when it is rotating at a constant speed. Design specifications require that the diameter of the shaft be uniform from A to D and that the angle of twist between A and D not exceed 1.45°. Knowing that τmax ≤ 60 MPa and G = 77.2 GPa, determine the minimum diameter shaft that can be used. (Round the final answer to one decimal place.)