And then how many of these combinations are there? If we are, once again, the god of probability, and out of 6 flips, we are choosing 4 that are going to end up heads. How many ways can I pick a group of 4? Well, once again, that's times 6 choose 4. And we figured out what that is. 6 choose 4 is 15. So this equals 15 times 0.8 to the fourth times 0.2 squared.