A traffic fanatic wants to estimate the maximum number of cars that can safely travel on a particular road at a given speed. He assumes that each car is 17 feet long, travels at speed s, and follows the car in front of it at a safe distance for that speed. He finds that the number N of cars that can pass a given spot per minute is modeled by the function N(s) 87s/19 + 19 (s/24)2|
At what speed can the greatest number of cars travel safely on that road?