Since A = {1, 2, 3, 4} and B = {5, 7, 9}. Therefore,

(i) A × B = {(1, 5), (1, 7), (1, 9), (2, 5), (2, 7), (2, 9), (3, 5), (3, 7), (3, 9), (4, 5), (4, 7), (4, 9)}

(ii) B × A = {(5, 1), (5, 2), (5, 3), (5, 4), (7, 1), (7, 2), (7, 3), (7, 4), (9, 1), (9, 2), (9, 3), (9, 4)}

(iii) No, A x B ≠ B x A. Since A x B and B x A do not have exactly the same ordered pairs.

(iv) n (A x B) = n (A) x n (B) = 4 x 3 = 12

n(B x A) = n(B) x n(A) = 4 x 3 = 12

Hence, n(A x B) = n(B x A)