What percentage of $\beta$-D-(+)-glucopyranose is found at equilibrium in the aqueous solution?

Ordinary glucose is $\alpha$-glucose, with a fresh aqueous solution has specific rotation, $[\alpha]_D=+110^{\circ}$. On keeping the solution for sometimes, $\alpha$-glucose slowly changes into an equilibrium mixture of $\alpha$-glucose (36\%) and $\beta$-glucose ( $64 \%$ ) and the mixture has specific rotation $+52.5^{\circ}$