$($a$)$ Determine the maximum shearing stress caused by a $40-$kip $*$in$.$ torque T in

the $3-$in$.-$diameter solid aluminum shaft shown. $($b$)$ Solve part a$,$ assuming that

the solid shaft has been replaced by a hollow shaft of the same outer diameter

and of $1-$in$.$ inner diameter.

The torques shown are exerted on pulleys A$,$B$,$ and C$.$ Knowing that

both shafts are solid, determine the maximum shearing stress in $($a$)$ shaft AB$,$

$($b$)$ shaft BC$.$