Assuming that the rates of return associated with a given asset investment are normally$$ distributed; that the expected$$ return, r overbar$,$ is $16\mathrm{.}9\%$; and that the coefficient of$$ variation, CV$,$ is $0\mathrm{.}39,$ answer the following$$ questions:

a$.$Find the standard deviation of$$ returns, sigma Subscript r$.$

b$.$Calculate the range of expected return outcomes associated with the following probabilities of$$ occurrence: $(1)68\%,(2)95\%,(3)99\%.$