You find a certain stock that had returns of $18$ percent, $-25$ percent, $21$ percent, and $7$

percent for four of the last five years. The average return of the stock over this period

was $9\mathrm{.}6$ percent.

a$.$ What was the stock's return for the missing year? $($Do not round intermediate

calculations and enter your answer as a percent rounded to $1$ decimal place, e$.$g$.,$

$32\mathrm{.}1.)$

b$.$ What is the standard deviation of the stock's returns? $($Do not round intermediate

calculations and enter your answer as a percent rounded to $2$ decimal places, e$.$g$.,$

$32\mathrm{.}16.)$