The next year's return for Zhang Ltd depends on the state of next year's economy. The return is predicted to be 16% in a boom, 5% in average conditions, and -12% (i.e. minus 12%) in a contraction. The probability of these outcomes is 40% chance of a boom, 50% chance of average conditions, and 10% chance of a contraction. Calculate the standard deviation of expected returns for Zhang Ltd based on this data.