At a certain instant in time, the number of cars, N, traveling on a portion of a certain highway can be estimated by the formula

N=$$20Lfrac{d}{(600+s^2)}$$where L is the number of lanes in the same direction, d is the length of the portion of the highway, in feet, and s is the average speed of the cars, in miles per hour. Based on the formula, what is the estimated number of cars traveling on a $$frac{1}{2}$$ mile portion of the highway if the highway has 2 lanes in the same direction and the average speed of the cars is 40 miles per hour? (5,280 feet = 1 mile)