(i) A × B: This is the Cartesian product of the sets A and B, which is the set of all ordered pairs (a, b) where a is an element of A and b is an element of B. In this case, A × B would be {(a,4), (a,5), (a,6), (b,4), (b,5), (b,6)}.

(ii) B × A: This is the Cartesian product of the sets B and A, which is the set of all ordered pairs (b, a) where b is an element of B and a is an element of A. In this case, B × A would be {(4,a), (4,b), (5,a), (5,b), (6,a), (6,b)}.

(iii) A × A: This is the Cartesian product of the set A with itself, which is the set of all ordered pairs (a, a) where a is an element of A. In this case, A × A would be {(a,a), (b,b)}.

(iv) B × B: This is the Cartesian product of the set B with itself, which is the set of all ordered pairs (b, b) where b is an element of B. In this case, B × B would be {(4,4), (4,5), (4,6), (5,4), (5,5), (5,6), (6,4), (6,5), (6,6)}.