Demand for devil's food whipped-cream layer cake at a local pastry shop can be approximated using a Poisson distribution with a mean of 4 per day. The manager estimates it costs $15 to prepare each cake. Fresh cakes sell for $18 . Day-old cakes sell for $15 each. Use Table C. a-1. Assume one-half of the day-old cakes are sold, and the rest thrown out. What service level is achieved in this situation? (Round your answer to 2 decimal places.) a-2. What stocking level is appropriate to achieve this service level