For alloys of two hypothetical metals P and Q, there exists a solid phase B, which is P-rich, and another solid phase ?, which is Q-rich. For two given alloy compositions, the mass fractions of a and B in equilibrium are:

Alloy composition in wt % Fraction a phase Fraction b phase 70 % P and 30 % Q 0.29 0.71 35 % P and 65 % Q 0.69 0.31

The mass fractions of both phases for the different compositions are given at the same temperature. Determine the composition of the solubility limit for both a and the b phases at this temperature