Alexander Proudfoot Co. was in the business of devising efficiency systems for industry. It told Sanitary Linen Service Co. that it could provide an improved system for Sanitary Linen that would save Sanitary Linen money. It made a contract with Sanitary Linen to provide a money-saving system. The system was put into operation, and Proudfoot was paid the amount due under the contract. The system failed to work and did not save money. Sanitary Linen sued to get the money back. Was it entitled to do so? [Sanitary Linen Service Co. v Alexander Proudfoot Co., 435 F2d 292 (5th Cir)]