this is a $2$d mechanics question.

The $40$mm diameter steel bar carries the bending moment M $=400$ Nm and a torque T$.$ If the yield strength of the steel is $280$ MPa determine the largest torque T that can be applied without causing yielding according to: a$)$ the maximum shear stress theory b$)$ the maximum distortion energy theory. Max shear stress theory compares the max shear stress with half the yield stress. Max distortion energy compares the von mises stress with the yield stress.the von mises stress is found:

a$\backslash$sqrt$($stress$1^(2)-$stress$1$ x stress $2+$ stress$2^(2))$

Fig Q$4$