A x B={(a,1),(a,2),(a,3),(b,1),(b,2),(b,3),(c,1),(c,2),(c,3),(d,1),(d,2),(d,3) }
A x B={(a,3),(a,2),(a, 5),(b,3),(b,2),(b,1),(c,3),(c,2),(c,1),(d,3),(d,2),(d,1) }
AxB={(a, b),(a, c),(a, d),(b,a),(b,c),(b,d),(c,a),(c,b),(c,d),(d,a),(d,b),(d,c) }
A x B={(a,1),(a,1),(a,1),(b,2),(b,2),(b,2),(c,3),(c,3),(c,3),(d,4),(d,4),(d,4)}
A x B={(1, a),(2, a),(3,a),(1, b),(2, b),(3, b),(1, c),(2, c),(3, c),(1, d),(2,d),(3, d) }