In the inventory model discussed in the text, we assumed a constant delivery cost that is independent of the amount delivered. Actually, in many cases, the cost varies in discrete amounts depending on the size of the truck needed, the number of platform cars required, and so forth. How would you modify the model in the text to take into account these changes?We also assumed a constant cost for raw materials. However, often bulk-order discounts are given. How would you incorporate these discount effects into the model?