$10-7.$ The last four years of returns for a stock are as follows:

Year $1234$

Return $-4\mathrm{.}4\%+27\mathrm{.}8\%+11\mathrm{.}6\%+3\mathrm{.}9\%$

a$.$ What is the average annual return?

b$.$ What is the variance of the stock$$s returns?

c$.$ What is the standard deviation of the stock$$s returns?