The tab$-$delimited text file M$423\_$A$1\_$S$3\_2025\_$Q$1\_$Q$2.$txt contains weekly data on the share prices of the Nvidia Corporation $($denoted NVDA$)$ and Advanced Micro Devices, Inc. $($AMD$),$ the American multinational technology companies; and the Standard and Poor$$s $500$ share index $($SP$500).$ The file also includes the simple weekly return on Nvidia shares $($R$1),$ the weekly return on AMD shares $($R$2),$ and the weekly return on the S&P $500$ index $($RM$).$ The data are from $30/11/2020$ to $2/12/2024.$ The share prices and index are in US dollars. The data are from finance.yahoo.com. $1($a$)$ Using the share returns for the period $7$ December $2020$ to $4$ December $2023,$ construct a portfolio consisting of Nvidia shares and AMD shares. Justify your choices. $1($b$)$ For the portfolio you formed in part $1($a$),$ examine the performance over the period $11$ December $2023$ to $2$ December $2024.$ Comment on your results.