A steel railroad track $($E$=29\backslash$times $10$ psi, a $=6\mathrm{.}5\backslash$times $10-6/\backslash$deg C$)$ was laid out at a temperature of $30\backslash$deg F$.$Determine the normal stress in the rail when the temperature reaches $125\backslash$deg F$,$ assuming that the rails $($a$)$ arewelded to form a continuous track, $($b$)$ are $39$ ft long with $$ in$.$ gaps between them.