XXX Company stocks part AA at its warehouse for supplying field service offices. The yearly demand for these parts is 6800 units. XXX Company estimates its annual holding cost for this item to be $ 10 per unit. The cost to place and process an order is $50. The company operates 300 days per year, and the lead time to receive an order is 5 days. The standard deviation of the demand is 15. a. Find the economic order quantity b. Find the total cost c. Determine the ROP needed if the manager wants an annual service level of 99.9 percent. Z= 3.1