If I take 20 moves to end up 10 moves to the right, then I have to make 15 right moves and 5 left moves. And likewise, if I take a total of 80 moves, if I take 80 flips of my coin to make me go left to right, in order to end up 10 to the right, I have to take 45 right moves and 35 left moves, in any order. And it'll end up with 10 to the right. So what I want to figure out is, as I start taking a bunch of total moves, it's like my total moves, I mean here I max it out at 170, but you could kind of say, if I started flipping this coin an infinite number of times, I want to figure out what's the probability that my final position is 10 to the right. And what I want to show you is that as you take more and more moves, the normal distribution becomes a better and better approximation for the binomial distribution. So right here, this calculates the binomial probability, just the way we did it before. And you could look at the cell to figure it out.