Customers send e-mails to a help desk of an online retailer every 5 minutes, on average, and the standard deviation of the interarrival time is 3 minutes. The online retailer has 6 employees answering e-mails. It takes on average 12 minutes to write a response e-mail. The standard deviation of the processing times is 5 minutes. (Do not round intermediate calculations. Round your answers to two decimal places.) (a) Estimate the average customer wait before being served.