A steel $E=29,200$ksi;$=6\mathrm{.}2\frac{{10}^{-6}}{}F$ pipe column $(1)$ with a cross$-$sectional area of $A_1=5\mathrm{.}10$ in$..{?}^2$ is connected at flange $B$ to an

aluminum alloy $E=10,400$ksi;$=13\mathrm{.}1\frac{{10}^{-6}}{}F$ pipe $(2)$ with a cross$-$sectional area of $A_2=3\mathrm{.}90in.{?}^2.$ The assembly $($shown in the

figure$)$ is connected to rigid supports at A and $C.$ It is initially unstressed at a temperature of $88F.$ Assume $L_1=135in.,L_2=173in.,P=$

$39$ kips.

$($a$)$ At what temperature will the normal stress in steel pipe $(1)$ be reduced to zero?

$($b$)$ Determine the normal stresses $($positive if tensile, negative if compressive$)$ in steel pipe $(1)$ and aluminum pipe $(2)$ when the

temperature reaches $-17F.$