5. Let n and k be integers such that 0

n} be the set 5. Let n and k be integers such that 0 k n, and let Zn consisting of the first n positive integers. Give a combinatorial proof of the q-Pascal recurrence n for the q-binomial coefficients by considering ordered set partitions of Zn+ of type (n k, k) in which n is in the set of size k or the set of size n k. (10 points)