At the drive through counter of a fast food outlet, an average of 20 cars wait in line. The manager wants to determine if the length of the line impacts the potential sales. her study reveals on average, 8 cars per minute try to enter the drive through area, but 40% of these cars are dismayed by the long line and simply move on without entering the line and placing orders. Assume that no car entering the line leaves without service. On average, how long does a car spend in the drive through line? Using littles law concept.