D$-$glucose exists as two epimeric cyclic hemiacetals: $-D-$glucopyranose $($left$,$ labeled hydroxy

group is in the axial position$)$ and $-$D$-$glucopyranose $($right$,$ the labeled hydroxy group is in

equatorial position$).$ The two anomers equilibrate via the open aldehyde form. Draw a curved arrow

mechanism to show the conversion of one anomer to the other under acid catalysis. Use $H-A$ to

represent the acid.