A shaft AC rotating at a constant speed carries a thin pulley of radius 𝑟 = 0.4 m at the end C which drives a belt. A motor is coupled at the end A of the shaft such that it applies a torque 𝑀z about the shaft axis without causing any bending moment. The shaft is mounted on narrow frictionless bearings at A and B where AB = BC = 𝐿 = 0.5 m. The taut and slack side tensions of the belt are 𝑇₁ = 300 N and 𝑇₂ = 100 N, respectively. The allowable shear stress for the shaft material is 80 MPa. The self-weights of the pulley and the shaft are negligible. Use the value of 𝜋 available in the on-screen virtual calculator. Neglecting shock and fatigue loading and assuming maximum shear stress theory, the minimum required shaft diameter is _______ mm (round off to 2 decimal places).