Suppose a stock has generated the following annual returns: $10\mathrm{.}0\%,-5\mathrm{.}0\%$ and $4\mathrm{.}0\%.$ What was the standard deviation of its returns? Answer in percent, rounded to two decimal places $($e$.$g$.,4\mathrm{.}32\%=4\mathrm{.}32).$