$13.$ The last four years of returns for a stock are as shown below:

a$.$ What is the average annual return? $\_\_\_\_\_\_\_\_\_\_\_\_.$

b$.$ What is the standard deviation of the stock's returns? $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.$

Year $1234$ Return $(\%)-3\mathrm{.}8328\mathrm{.}1811\mathrm{.}553\mathrm{.}53$