Citigroup Inc. on Wednesday confirmed that it will close Banamex USA, a small unit doing business across the U.S.-Mexico border, and agreed to pay $140 million to regulators who said the unit hadn’t done enough to protect itself from money launderers.
Analyze the relationship between 'Banamex' and 'Citigroup' within the context of the input sentence.
Options: stock exchange, operator, publisher, parent organization