|AxB| = |A| x |B| = 4 x 5 = 20
AxB = {(a,a),(a,b),(a,c),(a,m),(a,k),(b,a),(b,b),(b,c),(b,m),(b,k),(c,a),(c,b),(c,c),(c,m),(c,k),(d,a),(d,b),(d,c),(d,m),(d,k)}
|AxB| = |A| x |B| = 4 x 5 = 20
AxB = {(a,a),(a,b),(a,c),(a,m),(a,k),(b,a),(b,b),(b,c),(b,m),(b,k),(c,a),(c,b),(c,c),(c,m),(c,k),(d,a),(d,b),(d,c),(d,m),(d,k)}