The performance of the common stock of Apple Stores is highly dependent upon the state of the economy. In a boom economy,

the stock is expected to return $25\mathrm{.}0\%$ in comparison to $11\mathrm{.}0\%$ in a normal economy and negative $17\mathrm{.}0\%$ in a recessionary period.

The probability of a recession is $12\%.$ There is a $23\%$ chance of a boom economy. The remainder of the time the economy will be

at normal levels. What is the standard deviation of the returns on Apple stock?