Calculate the implicd volatility of soybean futures prices from the following information concerning a European put on soybean futures:
$$
\begin{array}{lc}
\hline \text { Current futures price } & 525 \\
\text { Exercise price } & 525 \\
\text { Risk-free rate } & 6 \% \text { per annum } \\
\text { Time to maturity } & 5 \text { months } \\
\text { Put price } & 20 \\
\hline
\end{array}
$$