Suppose you are an investor with a choice between three securities that are identical in every way except in terms of their rates of return and risk.
Investment A:
Total return = 10 percent with probability 50 percent
Total return = 20 percent with probability 50 percent
Investment B:
Total return = 12 percent with probability 40 percent
Total return = 18 percent with probability 60 percent
Investment C:
Total return = 5 percent with probability 60 percent
Total return = 25 percent with probability 40 percent
The standard deviation of investment A is ____ percent.