$9\mathrm{.}23\mathrm{.}10($a$)-($d$)$ Cite the phases that are present and the phase compositions for the following alloys:

$($a$)90wt\%Zn-10wt\%Cu$ at $400C(750F)$

$($b$)75wt\%Sn-25wt\%Pb$ at $175C(345F)$

$($c$)55wt\%Ag-45wt\%Cu$ at $)$

$($d$)30wt\%Pb-70wt\%Mg$ at $)$