Given the Temperature versus composition diagram for $C\frac{a}{S}$i binary system:

a$)$ Identify eutectics$($s$),$ congruent melting compounds, and incongruent melting compounds.

b$)$ If a $20\%$ by atom composition melt of silicon at $1500C$ is cooled down to $1000C,$ what phases $($and phase composition$)$ would be at

equilibrium? Estimate the relative amounts of each phase.

c$)$ Describe the equilibrium phases observed when an $80\%$ by atom composition $Si$ melt is cooled to $1030C.$ What phases, and relative

amounts, would be at equilibrium at a temperature $($i$)$ slightly higher than $1030C,$ temperature $($ii$)$ slightly lower than $1030C$