Several articles have applied the fuzzy set theory to discuss the fuzziness in the inventory problem. The problem that those articles address is related to the well-known economic order quantity (EOQ) problem, with some crisp parameters relaxed to fuzzy numbers. For example,Park [7] and Ishii and Konno [8] discuss the case of fuzzy cost coefficients. Roy and Maiti [9] develop a fuzzy EOQ model with a constraint of fuzzy storage capacity. Chang and Yao [lo] solve the economic order quantity with fuzzy backorders. Lee and Yao [ll] investigate the production
quantity model with fuzzy demand and fuzzy production quantities. Lee and Yao [12], Yao and Lee [13,14], and Chang [15] treat the decision variable “quantity” as fuzzy numbers, A common characteristic of these studies is that out-of-stock is permissible when a demand occurs. In other words, the demand occurring when the system is out of stock are backordered until a procurement arrives, and no extra costs are incurred. In this study, only one period is considered. It is impossible to backorder in the next period. Therefore, a penalty is attached to the unsatisfied demand.