It is worth mentioning that some optimization methods are very simple and others are too complex. For an up to date
review of different optimization methods in inventory field, see [4]. However, some of the optimization methods lack
the mathematical rigor and some of them are based on intuitive arguments. Furthermore, some of them do not have the
mathematical proof needed. In addition, all optimization methods that develop the EOQ and EPQ inventory models with
two classical backorders costs (linear and fixed) available until today are deficient or incomplete. Therefore, we find that in
both inventory models, there exists the need for developing a complete solution procedure for determining the optimal lot
size and backorders level.