please solve everything in the green using excel. thank you!

Using the data below estimate the monthly standard devation of the returns of a portfolio consisting of AA common-stock and BuB common stock. The numberi of shares of each stock in the portfolio are also given below. Enter your answer as a percent without the Wi round you final answer to two decimak. \begin{tabular}{ccr} \hline 8/1/2016 & 55.18 & 115.15 \\ \hline 9/1/2016 & 62.36 & 128.97 \\ \hline 10/1/2016 & 60.49 & 122.52 \\ 11/1/2016 & 64.12 & 142.12 \\ 12/1/2016 & 60.91 & 143.54 \\ 1/1/2017 & 58.47 & 142.11 \\ \hline 2/1/2017 & 66.66 & 130.74 \\ \hline 3/1/2017 & 68.66 & 121.59 \\ \hline 4/1/2017 & 67.97 & 113.08 \\ 5/1/2017 & 78.85 & 128.91 \\ \hline 5/1/2017 & 72.54 & 110.86 \\ \hline 7/1/2017 & 78.35 & 121.95 \\ 8/1/2017 & 90.10 & 141.46 \\ \hline 9/1/2017 & 72.98 & 168.33 \\ \hline 10/1/2017 & 66.41 & 136.35 \\ \hline 11/1/2017 & 74.38 & 151.35 \\ \hline 12/1/2017 & 87.02 & 160.43 \\ \hline 1/1/2018 & 100.08 & 142.78 \\ \hline 2/1/2018 & 83.06 & 114.23 \\ \hline 3/1/2018 & 76.42 & 108.52 \\ \hline 4/1/2018 & 68.78 & 99.83 \\ \hline 5/1/2018 & 67.40 & 117.80 \\ \hline 6/1/2018 & 78.19 & 115.45 \\ \hline 7/1/2018 & 82.10 & 92.36 \\ 8/1/2018 & 77.17 & 106.21 \\ \hline 9/1/2018 & 87.97 & 101.96 \\ 10/1/2018 & 71.26 & 99.92 \\ 11/1/2018 & 75.53 & 103.92 \\ 12/1/2018 & 66.47 & 101.84 \\ \hline 1/1/2019 & 65.81 & 113.05 \\ 2/1/2019 & 55.81 & 91.57 \\ 3/1/2019 & 59.96 & 93.40 \end{tabular} SD of portfolio