The past five monthly returns for PG&E are $-3\mathrm{.}39$ percent, $4\mathrm{.}43$ percent, $3\mathrm{.}99$ percent, $6\mathrm{.}80$ percent, and $3\mathrm{.}80$ percent. Compute the standard deviation of PG&E$\text{'}$s monthly returns. $($Do not round intermediate calculations and round your final answer to $2$ decimal places.$)$

Standard deviation