Consider a perishable product whose daily demand follows a normal distribution with mean 50 and standard deviation 5. Unsold units must be discarded. The retailer selling this product wants to maintain a 90% service level (i.e., the probability of fulfilling demand should be at least 0.9). a) How many units should the retailer order? b) What is the average number of unsold units each day? c) What is the fill rate