What is the volume fraction$($to two decimal places$)$ of the equilibrium $\backslash$theta phase at $20$oC for Al$-4\%$Cu $($by wt$.)?$ You can assume the equilibrium Al$(\backslash$alpha $)$ composition is Al$-0\mathrm{.}5\%$Cu $($by wt$.)$ and CuAl$2(\backslash$theta $)$ composition is Al$-54\%$Cu at $20$oC$.$ You can assume the densities of the Al$(\backslash$alpha $)$ and CuAl$2(\backslash$theta $)$ phases are $2\mathrm{.}700$ gm$/$cm$3$ and $4\mathrm{.}443$ gm$/$cm$3,$ respectively.