$($a$)$ Assuming that the maximum change in temperature at the site is expected to be $24$C$,$ find the change in length the span would undergo if it were free to expand.

cm

$($b$)$ Show that the stress on an object with Young's modulus Y when raised by $$T with its ends firmly fixed is given by $$Y$$T$.($Submit a file with a maximum size of $1$ MB$.)$