An example of customer-supplier duality is seen in the television repair process. The inputs to the process include spare parts, labor, testing equipment, etc. The output is a repaired television. The customers' role is to receive and ``consume'' (use) the output. However, the customers' role is also to provide the key input ± a broken television set. Therefore, the customer is both a supplier (of a broken television) and a consumer (of the repaired television). So also, health-care customers are suppliers (of illnesses and injuries) and consumers (of improved health). Landscaping customers are suppliers (of yards) and consumers (of improved scenery), etc. Many other examples of this duality will be introduced below inFigures 1 and 2.