Question 9: Let S1, S2,..., S26 be a sequence consisting of 26 subsets of the set 1,2,...,9) Assume that each of these 26 subsets consists of at most three elements Use the Pigeonhole Principle to prove that there exist two distinct indices i and j, such that rES i.e., the sum of the elements in S, is equal to the sum of the elements in S Hint: What are the possible values for 1ES, 2