Cite the phases that are present and the phase compositions for the following alloys: $($a$)15$ wt$\%$ Sn$85$ wt$\%$ Pb at $100\backslash$deg C $($b$)25$ wt$\%$ Pb$75$ wt$\%$ Mg at $425\backslash$deg C $($c$)55$ wt$\%$ Zn$45$ wt$\%$ Cu at $600\backslash$deg C $($d$)21\mathrm{.}7$ mol Mg and $35\mathrm{.}4$ mol Pb at $350\backslash$deg C$.$ Please check the related phase diagram in your text book. $($ans$.$ a$.$ C$=5$ wt$\%$ Sn$-95$ wt$\%$ Pb; C$=98$ wt$\%$ Sn$-2$ wt$\%$ Pb; b$.25$ wt$\%$ Pb$-75$ wt$\%$ Mg; c$.$ C$=51$ wt$\%$ Zn$-49$ wt$\%$ Cu; C$=58$ wt$\%$ Zn$-42$ wt$\%$ Cu; d$.$ CL$=94$ wt$\%$ Pb $6$ wt$\%$ Mg CMg$2$Pb $=81$ wt$\%$ Pb $19$ wt$\%$ Mg$)$