Scenario 9.15 A distributor of computer monitors purchases the monitors from an overseas supplier under a continuous review system. The average demand for a popular computer monitor is normally distributed with a mean of 50 units a day and a standard deviation of10 units a day. It costs $75 to process each order and there is a 16 day lead time The holding cost for each monitor is $20 per year and the distributor wishes to maintain a 90% service level. The distributor operates 300 days in a year. The distributor would like to use a periodic review inventory system to manage their inventory. Use the information in Scenario 9.15. What is the standard deviation of demand over the protection interval? 0 less than or equal to 30 units 0 greater than 40 units but less than or equal to 50 units 0 greater than 50 units O greater than 30 units but less than or equal to 40 units