The specific rotations of pure a- and -d-fructofuranose are 121 and 2133, respectively. Solutions of each isomer

Question:

The specific rotations of pure a- and β-d-fructofuranose are 121° and 2133°, respectively. Solutions of each isomer mutarotate to an equilibrium specific rotation of 292°. Assuming that no other forms are present, calculate the equilibrium concentrations of the two forms.