Suppose relation R(A,B,C) has the following tuples: A B C 1 2 3 4 2 3 4 5 6 2 5 3 1 2 6 and relation S(A,B,C) has the following tuples: A B C 2 5 3 2 5 4 4 5 6 1 5 4 Compute the union of R and S. Which of the following tuples DOES NOT appear in the result?