Problem $4$: What is the total elongation $($displacement of end $\backslash ($ C $\backslash )$ with respect to the fixed end $\backslash ($ A $\backslash ))$ of the bar $\backslash ($ A B C $\backslash )($diameter $80$ mm $),$ if part $\backslash ($ A B $\backslash )$ is made of bronze and part $\backslash ($ B C $\backslash )$ is made of steel. Young's moduli of bronze and steel: $96$ GPa and $200$ GPa $.$