Baseball Magazine, a domestic corporation, markets pictures of baseball players on its website. Its database server is in the Cayman Islands. Baseball fans access the Web page and use their credit cards to order their favorite player's picture. The server electronically transmits the credit card number to Baseball Magazine's U.S. bank account. Baseball Magazine sends an instruction to an independent mailing house in the U.S. to mail the photos to the fans from an inventory consigned by the players union. Baseball Magazine never actually takes title to the inventory. What is the source of Baseball Magazine's income?