Q$3$: $(10$ points$)$ Consider the tubular bar shown below which is loaded with a multiple torsional load. This bar is linear elastic and has three sections in which its outer radius and material properties are different.

$\backslash$table$[[$Section$,$Shear Modulus,Outer Radius,Inner Radius$],[1,15000$ ksi,$1\mathrm{.}5",0"\text{'}],[2,16000$ ksi,${2\mathrm{.}5}^{\text{'}\text{'}},{0\mathrm{.}8}^{\text{'}\text{'}}$