7. (a) In a group of 200 people, at least how many have names beginning with the same letter of the alphabet? (b) How many people must be in a room to ensure that at least 8 were born on the same day of the week? (c) If |A| = 10 and |B| = 100, how many functions from A to B are injective? (d) If |A| = 10 and |B| = 10, how many functions from A to B are bijective?