$n - Bu -\equiv\frac{(i) n-BuLi,n - C _{5} H _{11} Cl}{(ii) Lindlar\,\, cat, H _{2}}$
$n - C _{5} H _{11} Cl \downarrow$ (SN reaction)
$\begin{matrix}
CH-C{{O}_{2}}H \\
\,||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
CH-C{{O}_{2}}H \\
\end{matrix}\xrightarrow[(two\,mole)]{NaOH}(A)\xrightarrow{electrolysis}(B);$