A stock's returns have the following distribution:

Assume the risk-free rate is 3%. What is the stock's standard deviation of returns? 11.91% 12.71% 13.72% 16.79% 18.35%

\begin{tabular}{|l|r|r|} \hline Demand conditions & Probability & Rate of Return \\ \hline Weak & 10% & 24% \\ \hline Below average & 14% & 12% \\ \hline Average & 31% & 10% \\ \hline Above average & 24% & 18% \\ \hline Strong & 21% & 14% \\ \hline \end{tabular}