From the rate management page choose the Copy button on the rate you want to duplicate.
You will then land on the rate set-up page, with all the in-put fields pre-populated.
You can update the rate Name, and Pricing or any other details that need to be adjusted.
Choose 'Submit' to duplication.
Once you hit submit you'll be brought back to the rate management page with the new rate visible at the bottom of the list.
You can then re-order as needed.