In the context of the input sentence, determine the relationship between 'Banamex' and 'Citigroup'.
Options: member of, founded by, operator, subsidiary

Thu, Jul 23, 2015, 00:04 BST - UK Markets open in 7 hrs 56 mins Citigroup shuts Banamex USA, pays $140 mn in fines AFP – 40 minutes ago View Photo
operator