Keywords: two-level trade credit, deteriorating items, order quantity dependent credit, discount cash-flow, EOQCopyright © 2015 Universitas Ahmad Dahlan. All rights reserved.
IntroductionIn the traditional economic order quantity models assumed the purchaser must pay for the items as soon as the items received. However, in real markets, to stimulate retailer's ordering qualities the supplier allows a certain fixed permissible delay in payment to settle the amount. Similarly, a retailer may offer his/her customers a permissible delay period to settle the outstanding balance when he/she received a trade credit by the supplier, which is a two-level trade credit. Huang [1] was the first to explore an EOQ model under the two-level trade credit. Kreng and Tan [2] and Ouyang et al [3] proposed to determine the optimal replenishment decisions if the purchasers order quantity is greater than or equal to a predetermined quantity. Teng et al [4] extended the constant demand to a linear non-decreasing demand function of time and incorporate supplier offers a permissible delay linked to order quantity under two levels of trade credit. Teng et al [5] established an EOQ with trade credit financing for a linear nondecreasing demand function of time. Paulus [6] shed light on how search strategy can be used to gain the maximum benefit of information search activities. Feng et al [7] investigated the retailer's optimal cycle time and optimal payment time under the supplier's cash discount and trade credit policy within the EPQ framework. Wang et al [8] established an economic order quantity model for deteriorating items with maximum lifetime and credit period increasing demand and default risk. Liao [9] developed an inventory model by considering two levels of trade credit, limited storage capacity. Wu et al [10] discussed an economic order quantity model under two levels trade credit, and assumed deteriorating items have their expiration dates. Enda et al [11] presented a generic solution to the sensitive issue of PCI Compliance. Teng et al [12] proposed an EPQ model from the seller's prospective to determine his/her optimal trade credit period, and in his paper production cost declined and obeyed a learning curve phenomenon. However, the above inventory models did not consider the effects of the time value of money. In fact, as the value of money changes with time, it is necessary to take the effect of the time value of money on the inventory policy into consideration. Chang et al [13] investigated the DCF approach to establish an inventory model for deteriorating items with trade credit based on the order quantity. Chung and Liao [14] adopted the DCF approach to discuss the effect of trade credit depending on the ordering quantity. Liao and Huang [15] extended the inventory model to