Figure $1.$ Co$-$Fe phase diagram$\mathrm{.}2.$ Figure $1$ shows the binary Co$-$Fe phase diagram.

a$)$ What is the maximum solubility of iron to hcp cobalt? At which temperature is it achieved?

b$)$ What is the solubility of Fe to Co and Co to Fe at $1000$ K$?$

c$)$ What is the eutectoid point, corresponding equilibria and temperature in this system?

d$)$ Describe the equilibrium solidification $($i$.$e$.,$ the amounts and compositions of the phases as a function of temperature$)$ when $($i$)$ cobalt has been alloyed with $10$ at$-\%$ of iron and $($ii$)$ the nominal composition of the Co$-$Fe alloy is xFe $=0\mathrm{.}25($T $=1873$ K $=>$ T$=300$ K$).$