A store carries a popular food item. The average demand for this product is 15 units per day, with a standard deviation of 3.5 units. The stock is checked weekly. Suppose that at one particular occasion when the stock is being checked, there are 5 units in stock. The lead time to receive an order is 3 days. If the store wants to maintain a 95% service level, then the order size for this period is __________.
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