Assume that the equity risk premium is normally distributed with a population mean of $6$ percent and a population standard deviation of $18$ percent. Over the last four years, equity returns $($relative to the risk$-$free rate$)$ have averaged $2\mathrm{.}0$ percent. You have a large client who is very upset and claims that results this poor should never occur. Evaluate your client$$s concerns. A Construct a $95$ percent confidence interval around the population mean for a sample of four$-$year returns. B What is the probability of a $2\mathrm{.}0$ percent or lower average return over a four$-$year period I only need help with part B$.$ If you can show on excel on use formula text.