The US Transportation Security Administration (TSA) operates six "checkpoints" for screening departing passengers at the Grand Forks International Airport. Each checkpoint consists of a baggage conveyor belt, CTX scanning/imaging machine, and a walk-through metal detector for passengers to pass through. However, all six checkpoints are not necessarily operating all the time. This is because each checkpoint requires a team of three TSA employees to staff it, and there is not always a need to have six checkpoints running simultaneously. Passengers arriving at the airport are first met by a "greeter" who directs each passenger to one particular checkpoint that is in operation at that moment. Once "greeted," each passenger then joins their assigned checkpoint's single line to be screened, and it takes an average of one minute actually to screen each passenger through the checkpoint. The greeter's job is to divide the arriving passengers evenly between the checkpoints in operation. However, the rate at which passengers arrive at the airport and approach the greeter does vary with the time of day:

Time Period	Average Number of Passengers Arriving per Hour
5:00 AM to 6:00 AM	120
6:00 AM to 8:00 AM	280

TSA must maintain enough checkpoints such that the average delay experienced at checkpoint screening is less than 12 minutes. This delay includes both the time the passenger might wait to be screened, and the time being screened.

Recommend the number of checkpoints that TSA should operate during the various time intervals of the day first described in the table above, keeping in mind that TSA would prefer to minimize the staffing required.

Answer:

Time Period	Number of Check Points
5:00 AM to 6:00 AM
6:00 AM to 8:00 AM