A large call center is modeled as an M/M/c queue. There are two periods of demand throughout the day. The arrival rate in the first period is 300 calls per hour. The arrival rate in the second period is 480 calls per hour. During the first period, the call center employs 60 agents. During the second period, the call center employs 95 agents. The average service time is 10 minutes ( = 6/ hr).

(a) Using the square root approximation, which period experiences less delays (as measured by the probability that an arriving customer experiences a non-zero wait before receiving service)?

(b) Which period experiences less delays if the average service time is 5 minutes ( = 12/ hr) instead of 10 minutes?