Operations Management help needed. please check your work, provide explanation if possible. if it's right I'll give you a like.

A department store's customer service call center has 8 people working during every work day. A manager estimates that each worker is capable of solving an issue for 3 customers every hour. He also estimates that the call center receives a new complaint call every two minutes. To figure out the average wait time for each customer, the manager of the call center is attempting to use a M/M/S queuing model. The model will not currently run. Which of the following (if true) could explain the managers error and would allow the model to run if corrected (check all that apply). His estimates might be incorrect because the arrival rate exceeds the combined service rate for the system He forgot that the system has a maximum queue and that when the queue reached a certain length customers encounter a busy signal and are not placed in the queue The service time is actually normal so he should use an M/G/s model That the service center is actually opened 10 hours a day not 8