Problem: A small oil change shop uses an average of 80 litres of SW40 synthetic oil per day. Usage tends to be normally distributed with a standard deviation of 8 litres per day. Lead time is four days, and the desired service level is 92 percent. What amount of safety stock is appropriate under each of these conditions: (i) Oil is reordered every 45 days. (ii) A fixed order size of 2400 litres is used.