Calculate the following ratios for $2023,2022$ and $2021$: $($a$)$ net profit margin, gross profit margin, debtor $($receivable$)$ days, creditor $($payable$)$ days, return on capital employed, net asset turn over; $($b$)$ Based on the ratios calculated above, comment on the financial performance of Next plc over $3$ years; $($c$)$ Discuss how the company has reduced leverage $($borrowing$)$ to increase its profit during the period $2021$ to $2023.$