Suppose cars enter a one-way infinite length, infinite lane highway according to Poisson process with some rate = 1. The ith car to enter chooses a random velocity Vi miles per hour and continues to travel at this velocity. Assume that the Vi's are i.i.d. Vi ~ uniform(40, 120). Derive the distribution of the number of cars that are located in an interval (0, 10) kilometer at time 3 hour.