In Exercises 21–23 determine whether the relation with the directed graph shown is an equivalence relation.

Recall the following:
(i) A relation R on a set is called an equivalent relation if it is reflexive, symmetric and transitive.
(ii) A relation R is reflexive if and only if there is a loop at every vertex of the directed graph of R.
(iii) A relation R is symmetric if and only if for every edge...