Problem 5 The annual demand for an item is 20,000 units. The cost to process an order is $75 and the annual inventory holding cost is 25% of the purchasing cost per item per year. If the supplier offers the following price breaks for purchasing the item Quantity 1-499 500- 3,999 4,000 14,999 15,000 and Price $4.00 per unit $3.95 per unit $3.90 per unit more $3.85 per unit a. What is the optimal order quantity? b. What is the total annual cost at the optimal behavior? (including the purchasing cost) c. How frequently we should order (in days between orders)? Assume 250 working days/year d. How the optimal order quantity would be affected if the ordering cost increases to $200 per order