1.30)    Three relations are given on the set of all non-empty subsets of N.
                    In each case, say whether the relation is Reflexive or Symmetric or
                    it is Transitive.
 
            (a)    R is defined by: A R B if and only if A B.
            (b)    R is defined by: A R B if and only if if A  B is not equal to NULL.
            (c)    R is defined by: A R B if and only if 1  A  B.

            Solution:
 
            a)    It is reflexive.
                    It is NOT symmetric.
                    It is transitive.

            b)    It is reflexive.
                    It is symmetric.
                    it is transitive.

            c)    It is NOT reflexive.
                    It is symmetric.
                    It is transitive.