Solve clearly with explanation.

A gas station at a busy highway offers free air service for tires of cars that use the pump. The attendant checks tire pressure and inflates or deflates to the recommended level. On an average, the attendant takes 2 minutes to check one car. Cars arrive for the service at the rate of 17 per hour.

Q: The manager of the station is considering adding another attendant only if it will reduce the waiting time by more than 50%. What do you recommend?