part A Please:$)$

A circular cylindrical shaft is made of steel with yield stress ${}_{\text{y}\text{i}\text{e}\text{l}\text{d}}=700$MPa.

The shaft is subjected to a static bending moment $M=13\mathrm{.}0kN$ x m and a static torsional moment $T=30\mathrm{.}0kNm.$ Also, for the steel the modulus of elasticity is $E=200$GPa and Poisson's ratio is $v=0\mathrm{.}29.$ Employing a factor of safety of $2\mathrm{.}60,$ determine the minimum safe diameter for the shatt $($a$)$ using the octahedral shear stress. theory and $($b$)$ using the : maximum shear stress theory.