Determine the risk of each security using standard deviation

Question

Problem

It has been argued that stock risks can be managed through portfolio diversification. Kapito funds as an opportunity to invest in Haraka and Baraka stocks whose returns are indicated below;

Period            Haraka Returns       Baraka returns
1                              4%                             10%
2                              4%                             11%
3                             -8%                             -7%
4                              8%                             18%

Determine the risk of each security using standard deviation.