In: Math
Solve the following using a generating function:
Elizabeth is hosting a party inviting 7 friends. She bought gifts as the following: 8 teddy bears, 8 books, 5 watches. If she wants to give 16 gifts in total, where each person gets two gifts, with at least 2 teddy bears and 1 book. How many possible ways are there to choose from what she bought? Note: Don't distinguish between who gets what, just consider the 16 gifts.
Please only use a generating function, will upvote for that.