the daily demand for diet coke at heb is 90 bottles with a standard deviation of 7. the costs of placing the order are $10 and the annual holding costs are $1 per unit. the lead time is 6 days. assume the sales occur 365 days a year. the store wants to have a service level of a 0.95 probability of not stocking out during lead time). what should be the rop for this product