In manual order picking systems, order pickers walk or drive through a distribution warehouse in order to collect items … which are requested by (internal or external) customers. In order to perform these operations efficiently, it is usually … required that customer orders are combined into (more substantial) picking orders of limited size. The Order Batching Problem …

is on how many units to order; otherwise, there will be no order.An (r, S1, S2) policy with r < S2, S1 <= S2 is proposed … requested; if the higher price is quoted, then order up to S1, otherwise to S2. There are two cases, r < S1 or S1 <= r. In the … first case, every time the price is quoted, an order is placed. It is a single reorder point two order-up-to levels policy …