1. calculate the monthly returns for the two stocks '
2. Use excel to find variance and standard deviation of the returns on the two stocks
3. find covariance and correlation between the returns on the two stocks

\begin{tabular}{|r|r|r|} \hline Date & TD (US\$) & Shopify (US\$) \\ \hline 20180201 & 47.27 & 13.82 \\ \hline 20180301 & 46.35 & 12.46 \\ \hline 20180401 & 45.78 & 13.36 \\ \hline 20180501 & 48.06 & 14.81 \\ \hline 20180601 & 47.62 & 14.59 \\ \hline 20180701 & 48.71 & 13.82 \\ \hline 20180801 & 50.24 & 14.57 \\ \hline 20180901 & 50.49 & 16.45 \\ \hline 20181001 & 46.05 & 13.82 \\ \hline 20181101 & 46.33 & 15.27 \\ \hline 20181201 & 41.65 & 13.85 \\ \hline 20190101 & 47.17 & 16.85 \\ \hline 20190201 & 48.55 & 18.92 \\ \hline 20190301 & 45.97 & 20.66 \\ \hline 20190401 & 48.20 & 24.35 \\ \hline 20190501 & 46.70 & 27.49 \\ \hline 20190601 & 49.87 & 30.01 \\ \hline 20190701 & 49.94 & 31.79 \\ \hline 20190801 & 46.75 & 38.54 \\ \hline 20190901 & 50.26 & 31.17 \\ \hline \end{tabular}