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A supplier sells a popular auto part to car dealers. The weekly demand is approximately normal with the historical distribution of DN (63, 25) units over a 45-week operating year. Currently, the supplier pays $26 for each unit and sells each for $41. In addition, they estimate that the annual holding cost is 30 percent of the unit's cost (to the supplier). It costs approximately $25 to place an order (managerial and clerical costs). Assume a three-week lead time. a 16. What is the safety stock required per order under the optimal service level