Out of 4 people, why does ways to choose a 2-person committee overcount by 2 the ways to divide the 4 into 2 teams of 2?
Please see the sentence alongside my red line below. Why does part (a) overcount part (b) by a factor of c?
Scilicet, why aren't the answers to parts (a) and (b) the same? Whenever you choose a 2-person committee #1, the remaining unchosen 2 members automatically can form the 2-person committee #2.
Thus where's the overcounting?
Blitzstein. Introduction to Probability (2019 2 ed). p. 15.