Consider a copper$-$silver alloy of composition $25wt\%Ag-75wt\%Cu.$

a$.$ Supposed that this alloy is cooled to $780C($right above the eutectic temperature$).$

i$.$ What are the compositions of the two phases? $(1$ point$)$

ii$.$ Determine the mass fractions of a and $L$ phases. $(2$ points$)$

b$.$ Then the alloy is cooled to $778C($right below the eutectic temperature$).$

i$.$ What are the compositions of the two solid phases? $(1$ point$)$

ii$.$ Determine the mass fractions of the $$ and $$ phases. $(2$ points$)$