Texaco sold gasoline in Spokane, Washington to independent retailers and also to Gulf Oil, which operated its own filling stations and also sold to retailers. Texaco charged a substantially lower price to Gulf than to the independent retailers. These retailers sued Texaco, alleging that this price structure violated the Robinson Patman Act. At trial, the retailers presented evidence that they could not compete against Gulf. Texaco did not present evidence that the different prices it charged reflected the costs of serving these two sets of customers. Did Texaco violate the RPA?