6. Suppose that a new maneger for the local bookstore which discussed in Problem 5 assumes that the calculated stockout cost is incorrect due to difficulty in estimating the customer dissatisfaction cost. Instead of that, he adopts a service level of 99% with an assumption that the demand on the novel book during the lead time is normally distributed with a mean of 140 books and a variance of 16 (book). Determine the updated safety stock level