An ester ${\text{A(C}}_{\text{4}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}\text{),}$ on treatment with excess methyl magnesium chloride followed by acidification, gives an alcohol $\text{B}$ as the sole organic product. Alcohol $\text{B,}$ on oxidation with $\text{NaOCl}$ followed by acidification, gives acetic acid. Ester $\text{A}$ is: