What kind of information one can obtain from a phase diagram?

With a figure of an isomorphous binary phase diagram describe inverse level rule.

For $90$ wt$.\%$ Sn$-10$ wt$.\%Pb$ alloy at $(400F).$

a$.$ What phase$($s$)$ is $($are$)$ present?

b$.$ What is $($are$)$ the composition$($s$)$ of the phase$($s$)?$

c$.$ Write the eutectic reaction for this alloy?

d$.$ calculate the relative amount of each phase present in terms of mass fraction.