The solid aluminum shaft has a diameter of $50 \mathrm{mm}$ and an allowable shear stress of $\tau_{\text {allow }}=60$ MPa. Determine the largest torque $T_{1}$ that can be applied to the shaft if it is also subjected to the other torsional loadings. It is required that $\mathbf{T}_{1}$ act in the direction shown. Also, determine the maximum shear stress within regions $C D$ and $D E$