A U.S. appeals court on Monday weighed whether to uphold the approval of an estimated $5.7 billion antitrust settlement by MasterCard Inc (MA.N) and Visa Inc (V.N) with merchants over credit card fees despite the objection of several major retailers. A lawyer for retailers including Target Corp (TGT.N) and Amazon.com Inc (AMZN.O) urged the 2nd U.S. Circuit Court of Appeals in New York to reject the deal, saying it forces merchants to give up their rights to sue over various policies and practices.