Answer and Explanation:
The calculations of the stock return for the missing year is shown below:
a. Let us assume the fifth year stock return be x
As we know that
Average rate of return = Total returns ÷ number of years
0.12 = (0.1 - 0.11 + 0.21 + 0.22 + x) ÷ 5
So after solving this, the x is 14%
b. Now the standard deviation of the stock return is presented in the excel spreadsheet
The standard deviation is 13.40%