As a final illustration, consider the two sets A = {a1, a2} and B = {b1, b2, b3, b4} (Fig 2.3). A x B = {(a1, b1), (a1, b2), (a1, b3), (a1, b4), (a2, b1), (a2, b2), (a2, b3), (a2, b4)}. The 8 ordered pairs thus formed can represent the position of points in the plane if A and B are subsets of the set of real numbers and it is obvious that the point in the position (a1, b2) will be distinct from the point in the position (b2, a1).