So five choose one is equal to five factorial over one factorial, which is just one, times five minus four, sorry five minus one factorial, which is equal to five factorial over four factorial, which is just going to be equal to five. All right, we're making good progress. So now let in purple, let's think about the probability that our random variable X is equal to two. Well this is going to be equal to, and now I'll actually resort to the combinatorics. So this is, you have five flips, and you're choosing two of them to be heads over 32 equally likely possibilities. So this is the number of possibilities that result in two heads. Two of the five flips have chosen to be heads.