A regional cellphone sales manager is deciding how many people to hire for a sales office. Data shows sales associates take 15 minutes per customer. The service time follows an exponential distribution. The arrival rate is expected to be 12 people per hour and will follow a Poisson distribution. This particular branch is scheduled to have 4 sales associates. What is the average time people will wait in line in minutes before being seen by a sales associate? Calculate your answer to three decimal places