Demand for a coffee cup is normally distributed with a mean of 18 units per week and a standard deviation in weekly demand of 5 units. The lead time is 2 weeks, and the business operates 52 weeks per year. The continuous review system called for an EOQ of 75 units and a cycle-service level of 90 percent (for 90% service level, assume the value of z = 1.28). What is the time between reviews under periodic review system (P system)