Let A and B be sets with |A| = 10 and |B| = 7. What can we say about |A ∪ B|? In particular, find two numbers x and y for which we can be sure that x ≤ |A ∪ B| ≤ y and then find specific sets A and B so that |A ∪ B| = x and another pair of sets so that |A ∪ B| = y.