On the Optimality of Generalized (s,S) Policies

A standard inventory model is examined with a concave increasing ordering cost function rather than simply a linear one with a setup cost. A generalized (s, S) policy is shown to be optimal in the n-period problem. A generalization of k-convex and quasi-convex functions to quasi-k-convex functions is required in the process. The probability densities of demand must be one-sided Pólya densities.