$($c$)$ For the Mg$-$Pb binary phase diagram shown in Figure $4,$ label all the two$-$phase regions and identify the eutectic transformations on the graph, and in reaction form, with temperature and composition specified.

$($d$)$ Calculate the mass fraction of the phase$($s$)$ present for a $20$ wt$\%$ Pb $-80$ wt$\%$ Mg alloy at $700\backslash$deg C$,600\backslash$deg C$,500\backslash$deg C$,$ and $200\backslash$deg C$.$ Draw the microstructure at each state point.Composition $($at$\%$ Pb$)$