QUESTION $8$ The daily sales of a peanut butter at Power's Grocery are normally distributed, with a mean of $12$ jars and a standard deviation of $4.$ The manager checks the inventories on shelves and places an order every three days. Delivery lead time is two days and they carry $21$ jars for safety stock. If there are $4$ jars on the shelf when an order is placed, how much should the store order? $77323681$