The performance of the common stock of Creekside Stores is highly dependent upon the state of the economy. In a boom economy, the stock is expected to return 24% in comparison to 11% in a normal economy and a negative 18% in a recessionary period. The probability of a recession is 10%. There is a 20% 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 Creekside stock?