A Steel Tube with Diameters $d_{2}=86 \mathrm{~mm} \text { and } d_{1}=52 \mathrm{~mm}$

A steel tube with diameters $d_{2}=86 \mathrm{~mm} \text { and } d_{1}=52 \mathrm{~mm}$ is twisted by torques at the ends. The diameter of a solid steel shaft that
Resists the same torque at the same maximum shear stress is approxi-
Mately: (A) $56 \mathrm{~mm}$
(B) $62 \mathrm{~mm}$
(C) $75 \mathrm{~mm}$
(D) $82 \mathrm{~mm}$