$4$ of $4$

$4.(8$pts$)$ For the following, consider the above $Pb-Sn$ phase diagram, for $C_0=80wt\%Sn,$ i$.$ What is the composition of each phase $(wt\%Sn$ just above $T_E?$

ii$.$ What is the relative weight fraction of each phase just above $T_E?$

iii. Upon cooling below $T_E,$ what is the proeutectoid phase?

iv$.$ Sketch the resulting microstructure $($indicating each phase$)$ when cooled to just below $T_E.$