The returns on the common stock of New Image Products are quite cyclical. In a boom economy, the stock is expected to return $20$ percent in comparison to $12$ percent in a normal economy and a negative $10$ percent in a recessionary period. The probability of a recession is $15$ percent while the probability of a boom is $25$ percent. What is the standard deviation of the returns on this stock? $($Do not round intermediate calculations and enter your answer as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$