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. So this is the probability of 4 out of 6 heads given an unfair coin. So what's the total probability of getting 4 out of 6 heads? Well, it's going to be the probability of getting the fair coin, which is 1 third, times the probability of getting 4 out of 6 heads given the fair coin.