Consider a pair of stocks: Visa and MasterCard and do following three questions:

$(1)$ Use getSymbols function $($quantmod package$)$ to retrieve the data from $01/02/2020-12/31/2022,$ and plot the log prices. $($you can use either close price or adjusted price$)$

$(2)$ Use the egcm package to construct the price spread, and plot the spread.

$(3)$ Construct a long$-$short trading strategy and perform backtesting. How is the performance of the pairs trading, for training and testing sample?