고체역학 (Beer) — Torsion: Problem 3.28

3.28 A torque \(T = 900 \text{ N}\cdot\text{m}\) is applied to shaft \(AB\) of the gear train shown. Knowing that the allowable shearing stress is \(80 \text{ MPa}\), determine the required diameter of (a) shaft \(AB\), (b) shaft \(CD\), (c) shaft \(EF\).