Olney Wireless stock is quite cyclical. In a boom economy, the stock is

expected to return $30$ percent in comparison to $12$ percent in a normal

economy and a negative $20$ percent in a recessionary period. The probability of

a recession is $15$ percent while it is $30$ percent for a booming economy. The

remainder of the time, the economy will be at normal levels. What is the

standard deviation of the returns?

$17\mathrm{.}46\%$

$10\mathrm{.}05\%$

$15\mathrm{.}83\%$

$12\mathrm{.}60\%$