Give a story proof that (see attachment) for all positive integers n. Hint: Consider choosing a committee of size n from two groups of size n each, where only one of the two groups has people eligible...

Give a story proof that (see attachment) for all positive integers n. Hint: Consider choosing a committee of size n from two groups of size n each, where only one of the two groups has people eligible to become president.
Give a story proof that E (n) 2 = n en — 1 \ ,k k n — 1 ) k=1