Definition 2.6: letr be a relation from a to B. The domain of r denoted by Dom(R), is the set of elements in A that are related to some element in B. The range of R, denoted by Ran(R), is the set of elements in b that are related to some element in a Dom RcA, Ran robDefinition 2.6: Let R be a relation from A to B. The domain of R, denoted by Dom(R), is the set of elements in A that are related to some element in B. The range of R, denoted by Ran(R), is the set of elements in B that are related to some element in A. Dom RA,Ran RB