A telephone customer service center wants to ensure that the majority of customer calls are answered within a reasonable amount of wait time. Based on customer feedback, the company has determined that this wait time is between 10 and 45 seconds. A large sample of data points collected revealed an average wait time of 31 seconds with a standard deviation of 4.5 seconds.
Calculate the process capability index and advise if the process is at an acceptable level for an existing process (defend your answer).