The federal funds interest rate is in percent form so convert it to decimal (i. e., fractional) form. Then, for the S&P 500 and long term treasury bonds ETF assets, compute the returns using the following formula: rt = pt pt1 pt1 where rt is the return at time t, pt is the asset price at time t, and pt1 is the asset price at time t 1 (i. e., the previous period). Add both sets of returns to your training set tibble. These returns are also called total returns. Construct a single time series plot with the returns for both assets plotted. Add a dotted, horizontal line at y = 0 to the plot. Compare the two returns series. What do you see?