The index model has been estimated from the excess returns for stock A with the following results:

$R_A=12\mathrm{.}00\%+1\mathrm{.}55R_M+e_A$

${}_M=24\mathrm{.}00\%$

$(e_A)=18\mathrm{.}50\%$

What is the standard deviation of the return for stock A$?($Round your answer to $2$ decimal places.$)$