A local utility has a customer service call center that takes 3 types of calls: (1) Billing inquiries (2) Requests for change of service, and (3) Technical problems. During the busiest time of day, they receive on average 25 calls per hour for billing inquiries, 50 calls per hour for change of service, and 2.5 calls per hour dealing with technical problems. The number of calls per hour of each type has Poisson distribution, which implies the time between calls of each type has exponential distribution. The service time for each type of call has exponential distribution, with the following average time per call: • Billing inquiries: 3 minutes • Service change: 3 minutes • Technical problems: 15 minutes.