. Let r be a relation with schema (A, B, C) and contains 20 tuples. If r has exactly 7 tuples where A is X1, exactly 13 tuples where B is Y2 and exactly 5 tuples where A is X1 and B is Y2. What is the number of tuples in the following relation? 3 A=X1 B=Y2 (r) - represents sigma (select operation)