Neve Commercial Bank is the only bank in the town of York, Pennsylvania. On a typical Friday, an average of 10 customers per hour arrive at the bank to transact business. There is one teller at the bank, and the average time required to transact business is 4 minutes. It is assumed that service times may be described by the negative exponential distribution. A single line would be used, and the customer at the front of the line would go to the first available bank teller. If a single teller is used:

CEO Benjamin Neve is considering adding a second teller (who would work at the same rate as the first) to reduce the waiting time for customers. He assumes that this will cut the waiting time in half.

If a second teller is added, the average time a customer spends in the system = minutes (round your response to two decimal places).