Demand for walnut fudge ice cream at the Sweet Cream Dairy can be approximated by a normal distribution with a mean of 18 gallons per week and a standard deviation of 6.7 gallons per week. The new manager desires a service level of 90 percent. Lead time is two days, and the dairy is open seven days a week. (Hint: Work in terms of weeks.) Use Table B and Table B1. a) How many days of supply are on hand at the ROP, assuming average demand?