Chapter 20, Problem 20.50P

Treatment of ketone A with ethynylithium $\left(\text{HC}\equiv \text{CLi}\right)$ followed by ${\text{D}}_{\text{3}}{\text{O}}^{\text{+}}$ afforded a compound B of molecular formula ${\text{C}}_{\text{12}}{\text{H}}_{\text{13}}{\text{DO}}_{\text{3}}$ which have an IR absorption at approximately ${\text{1715 cm}}^{\text{-1}}$ . What is the structure of B and how is it formed?