A 60 wt% Pb-40 wt% Mg alloy is rapidly quenched to room temperature from an elevated temperature

Question:

A 60 wt% Pb-40 wt% Mg alloy is rapidly quenched to room temperature from an elevated temperature in such a way that the high-temperature microstructure is preserved. This microstructure is found to consist of the α phase and Mg2Pb, having respective mass fractions of 0.42 and 0.58. Determine the approximate temperature from which the alloy was quenched.