solution:
The activity ∗ characterized on the set {1, 2, 3, 4, 5} by a ∗ b = L.C.M. of an and b
Assume, a = 2 and b = 3
2 * 3 = L.C.M. of 2 and 3 = 6
However, 6 doesn’t has a place with the set A.
In this manner, given activity * is anything but a paired activity.