$3.$a The solid cylindrical shaft with dimensions as shown consists of two materials, Nylon

for $AB$ and Aluminum for section BC$.$ An external toque $T$ is applied at point B$.$ At A and C

the shaft is rigidly held and not allowed to rotate by the supports.

As the torque $($ T $)$ applied at point B increases, at what value of T does yielding begin

in the shaft? Explain in which section and show your work.

Assume the following:

$G_{AL}=26\mathrm{.}0$GPa

${}_{\text{y}\text{r}\text{e}\text{l}\text{d}AL}=120$MPa