Some people purchase expensive water conditioners to reduce the mineral content in their water, enhance the effectiveness of soaps and detergents, and reduce deposits in plumbing systems. A manufacturer of a certain brand will often designate a single plumbing company to be its sole supplier in a geographic area and provide special training for that dealer to service the product. The product warranty will also often state explicitly that the customer should request service from the dealer if there is a problem and use parts made only by the manufacturer. What are the benefits to the manufacturer and the dealer from entering into such an agreement?