고체역학 (Gere) — Torsion: Problem R-3.9

R-3.9 A gear shaft transmits torques $T_A = 975 \text{ N}\cdot\text{m}$, $T_B = 1750 \text{ N}\cdot\text{m}$, $T_C = 650 \text{ N}\cdot\text{m}$, and $T_D = 125 \text{ N}\cdot\text{m}$. If the allowable shear stress is $50 \text{ MPa}$, the required shaft diameter is approximately: (A) $38 \text{ mm}$ (B) $44 \text{ mm}$ (C) $46 \text{ mm}$ (D) $48 \text{ mm}$