Bob and Marge entered into a contract for the sale of 100 widgets. Marge was to pay Bob $200 for the widgets. Marge paid Bob $100 and Bob delivered the widgets. Subsequently, Bob made an assignment of his rights under the contract to Laura to whom he owed $200. Bob delivered notice of the assignment to Marge. Laura demanded $200 from Marge. Marge refused to pay and Laura sued her. DECIDE.