B could shake C's hand. B could shake, whoops. B could shake D's hand. And you can say C could shake A's hand, C could shake B's hand, C could shake, C could shake D's hand. and you could say D could shake A's hand, D could shake B's hand, D could shake C's hand. And this is 12 right over here, and this is a permutations. If D shaking C's hand was actually different than C shaking D's hand, then we would count 12.