buffet

Q: What is the ruling on buying from open buffet restaurants, where the customer pays a set amount and eats an unknown amount of food that is not known to the buyer or the purchaser, rather he may eat until he is full?

Q: Zaid has paid a hotel for buffet food. The hotel lets Zaid take whatever amount of food he wants to eat to his room. Will it be permissible for Zaid to share some of his food with his family members who are staying with him in his room?