Abstract
This paper deals with a production planning model in which many goods are produced by using a single line.Constantly durable demands which any feasible production plan must fulfill are given for the products throughout a period considered.In such a model, the inventory cost is an important factor to estimate the efficiency of the plan.Taking Japanese business customs into account, we notice that the interest on inventory changes discretely depending on the date of payment.Our aim is to obtain a plan which minimizes the sum of the set-up cost and the above mentioned inventory cost.
