What is the name of the functional group enclosed in the oval in the following structure? 
Definitions:
Truth-in-Lending Act
A U.S. federal law designed to promote the informed use of consumer credit by requiring disclosures about its terms and cost.
Deferred Payment Plan
A payment arrangement that allows a purchaser to pay for goods or services at a later date, often after receiving some form of benefit from them.
Retroactive APR
Annual Percentage Rate that is applied to charges made previously, often after a promotional period ends or due to a late payment.
Monthly Periodic Rate
The APR divided by 12; the rate of interest charged each month.
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