Kelly's Service Station does a large business in tune-ups. Demand has been averaging 210 spark plugs per week. Holding costs are $.01 per plug per week and reorder costs are estimated at $10 per order.
Kelly does not want to be out of stock on more than 1% of his orders. There is a one-day delivery time. The standard deviation of demand is five plugs per day. Assume a normal distribution of demand during lead time and a 7-day work week.