  In this paper, we propose an inventory model where items are inspected
through multiple screening processes before delivery to customers. Each
screening process has independent screening rate and defective percentage.
Defective items screened out are stored and then returned to supplier. Shortage
backordering are also allowed in the model. Two approaches are used to obtain
the closed-form optimal order size and the maximum backordering quantity.
Numerical examples are also provided to demonstrate the use of the model.
