Session $10-$ Q$4$

The system below has appropriately balanced masses to be in equilibrium. If shaft $AB$ and $CD($not including the gears$)$ have diameters of $1\mathrm{.}0cm,m_2=10kg,g=9\mathrm{.}8\frac{m}{s^2},a_2=5cm,l_2=8cm,l_1=8cm,\frac{r_2}{r_1}=2\mathrm{.}0,$ and the elastic modulus of the material in the shaft is $200$ GPa with a Poisson's ratio of $0\mathrm{.}30,$ what is the angle of twist going from $A$ to $D$ in degrees? You might refer to $2015$ Exam $1.$