The Economic Order Quantity model includes positive delivery lead time and demand uncertainty. A U.S.-based firm places product orders with its supplier in Asia using this model. Demands for the product that the firm resells to U.S. consumers arrive at a constant rate but they are uncertain. Currently the product units are shipped by air, but the firm is considering switching to an ocean carrier option, which will increase the delivery lead time. In each case, the firm expects to carry safety stock inventory. At what interval and lead time should the order be placed?