isds 3115 math problem i dont understand how i keep getting it wrong?

A cigar company stocks Cuban cigars that have variable lead times because of the difficulty in importing the product. Lead time is normally distributed with an average of 8 weeks and a standard deviation of 3 weeks. Average demand is also normally distributed with a mean of 225 cigars per week and a standard deviation of 23 cigars. a. For a 98% service level, what is the ROP? b. What is the ROP for a 90% service level? c. Explain what these two service level mean. Which is preferable?