Please show full steps in excel with formulas, I will provide thumbs up! :) Please dont copy answer from another question

4. Demand for Hagen-Dazs ice creams at a grocery store can be approximated by normal distribution with a mean of 21 liters per week and a standard deviation of 3.5 liters per week. The ice cream is purchased from a local supplier. The store manager desires a cycle-service level of 90 percent. Lead time from the producer is two days. The store is open seven days a week. If the P system is used, what should be the order quantity if the order interval is 7 days and the inventory position is 8 liters at the time of order