For the shaft shown below $T_A=4\mathrm{.}9kN-m,T_B=12\mathrm{.}0kN-m,L_1=2\mathrm{.}1m,$ and $L_2=1\mathrm{.}9m.$ The shear moduli are $19$GPa and $21$GPA for the left and right segments, respectively. The polar moments of inertia are $2\mathrm{.}2{10}^{6}m{m}^4$ and $2\mathrm{.}0{10}^{6}m{m}^4$ for the left and right segments, respectively. Determine the rotation of the shaft at the free end in radians $($magnitude only$).$

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