Find the set A n B. U = {1, 2, 3, 4, 5, 6, 7, 8, 9} A = {2, 3, 6, 7} B = {2, 3, 9} . . . Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. AnB= (Use a comma to separate answers as needed.) O B. An B is the empty set.Let U = {3, 15, 6, 12, 11, 17, 21, 22} A = {3, 21, 22} C = {15, 6, 12, 11, 17} Find A U C'. . . . Choose the correct answer below, and, if necessary, fill in the answer box to complete your choice. O A. AUC' = 4 (Use a comma to separate answers as needed.) O B. A U C' is the empty set