depicted in Figure4.
Again, we consider the example of television repair with respect to the Figure 4 model. A customer supplies a broken television to the television repair shop. The shop also receives parts and equipment inputs from other suppliers. After repairing the television it is returned to the customer. In this process the television was supplied by the repair shop who got it from the customer. Therefore, the customers are their own second-tier supplier (the supplier of their supplier), since they supplied the television that is ultimately delivered back to them. Other examples of single-level bidirectional supply chains are shownin Figure1.