Question $3$: An aluminium$-$alloy strut for a light aircraft having the cross$-$section shown in Figure

Q$3$ is $3m$ in length. If the shear stress is not to exceed $30M\frac{N}{m^2}$ and the applied torque is $134$

$Nm,$ determine the required thickness $t$ of the metal. What is the angle of twist? G $=28G\frac{N}{m^2}.$