So just to review a little bit of the last video, we said we're trying to model out the probability distribution of how many cars might pass in an hour. And the first thing we did is we sat at that intersection, and we found a pretty good expected value of our random variable, and this random variable, just to go back to the top, we defined the random variable as the number of cars that pass in an hour at a certain point on a certain road, and we said that we measure it a bunch. We sat out there a bunch of hours, and we got a pretty good estimate of this, and we say it's lambda. And we said, OK, we wanted to model it as a binomial distribution. So if this is a binomial distribution, then this lambda would be equal to the number of trials times the probability of success per trial. And so if we could view a trial as an interval of time, this is the total number of successes in an hour. Success in hour, and so this would be success in an smaller interval, an interval, and this would be the probability of success in that smaller interval.