A hollow shaft of outside diameter 50 mm and inside diameter 20 mm is subjected to a torque of T N.m and a bending moment of 0.5 T N.m. If the tensile yield stress of the shaft material is 250 N/mm2, what is the maximum permissible value of T to avoid failure according to Tresca’s failure theory? Take a factor of safety 2.0 for a given application.