Using Fig $10\mathrm{.}3,$ consider a copper$-$nickel alloy of composition $70wt\%Ni-30wt\%Cu$

is slowly heated from a temperature of $1300C(2370F).$

$($a$)$ At what temperature does the first liquid phase form?

$($b$)$ What is the composition of this liquid phase?

$($c$)$ At what temperature does complete melting of the alloy occur?

$($d$)$ What is the composition of the last solid remaining prior to complete melting?