Consider the drive-through window at the It may be reasonably modeled as a first-come first-serve, single-server queuing system with random arrivals at the rate of 12 customers per hour and exponential service times with a mean service time of 4 minutes. Assume that both the system capacity and calling source are infinite. To the nearest first decimal place, what is the expected total number of cars being served or waiting to be served in steady state? 

• None of the other choices
• 3.5 cars
• 5.0 cars
• 4.0 cars