a
\(\begin{gathered}
{\text{pOH}} = {{\text{p}}^{{{\text{K}}_{\text{a}}}}} + \log \frac{{Salt - (Acid)}}{{Acid + (Acid)}} \hfill \\
pOH = - \log (2 \times {10^{ - 5}}) + \log \frac{{0.2 - 0.001}}{{0.2 \times 0.001}}\,\,\,\,\,\,O{H^ - } = 2 \times {10^{ - 5}} \hfill \\
\end{gathered} \)