Consider a customer walking into a Wal-Mart store to purchase detergent. The supply chain begins with the customer and their need for detergent. The next stage of this supply chain is the Wal-Mart retail store that the customer visits Wal-Mart stocks its shelves using inventory that may have been supplied from a finished-goods warehouse that Wal-Mart manages or from a distributor using trucks supplied by a third party. The distributor in turn is stocked by the manufacturer (say Product and Gamble in this case ). The P&G manufacturing plant receives raw material from a variety of suppliers who may themselves have been supplied by lower tier suppliers. For example, packaging material may come from Tenneco packaging while Tenneco receives raw material to manufacture the packaging from other suppliers. This supply chain is illustrated in Figure 1.1