In how many ways can 12 indistinguishable apples and 1 orange be distributed among three children in such a way that each child gets at least one piece of fruit? Consider the multiset {n, a, l, 2, 3, ..., n} of size 2n. Determine the number of its n-combinations. Consider the multiset {n, a, n, b, 1, 2, 3, ..., n+1} of size 3n+1. Determine the number of its n-combinations.