Final answer:
A traffic jam on the one mile stretch of highway is expected when the arrival rate reaches 200 cars per minute, given that each car takes one minute to travel the mile at the speed limit of 60 miles per hour.
Step-by-step explanation:
The question asks at what arrival rate of cars a traffic jam can be expected on a one mile stretch of highway when the congestion threshold is 200 cars. Given that the arrival rate is 50 cars per minute and will rise to 300 cars per minute by 6PM, we need to determine the arrival rate at which 200 cars would simultaneously be on the one-mile stretch, assuming they are traveling at the normal speed limit of 60 miles per hour. Since a car covers one mile in one minute at the speed of 60 miles per hour, it means the road will reach maximum capacity and get congested when the arrival rate is 200 cars per minute, not the 50 cars per minute as it is at 1PM.