Now, repeat the sorting you did in part (a) for all beginning-of-the-year and middle- of-the-year time points. Namely, just as you sorted your chosen stocks into 5 groups on January 1, 2013 based on their past-12-month average returns, you repeat this process on July 1, 2013 (where your sorting is based on average monthly returns from July 2012 to June 2013), and then on January 1, 2014, and then on July 1, 2014, and so on and so forth. The last sorting you do should be with respect to July 1, 2022. In other words, you should obtain 20 sets of sorted groups in total. Note that group compositions may change from one sorting to another.