At a taxi stand, there is usually a line of taxicabs waiting to pickup passengers. The number of taxicabs there varies in time, but eventually, they all leave with a passenger. On average, there are 10 cars at the taxi stand. A car arrives at the taxi stand to join the line every 5 minutes on average. What is the average time a taxi driver has to wait until s/he departs with a customer? Provide your answer in minutes. a