Consider a walk-and-pick system, where the total aisle length to be provided is fixed at 1440. That is, if there are 10 aisles (M  10), then each aisle must be 144 long; if there are 20 aisles, each aisle must be 72 long; and so on. Including shelving on either side, and the aisle clearance itself, suppose the aisle width is equal to 10 per aisle. For example, for M  10, the warehouse width will be 100. Using the results given for walkand-

pick systems, determine the optimum number of aisles (M) that would minimize the total expected walking distance per order.