Please answer part a$-$b$.$ Show all your work and calculations Q$3.[]$

Two portions of the rod ABC are welded together, and

two forces are applied axially as shown.

$($a$)$ If the allowable stress for section $AB$ is ${}_{-}$allow$1$

$=175$MPa and that for section BC is ${}_{-}$allow $2=$

$150$ MPa $,$ determine the smallest allowable

diameters, d $1$ and d $2$ in millimeters.

$($b$)$ If the Young's modulus E$=73$ GPa for both

sections, calculate the total deformation in

millimeters at point C due to the forces applied.