Given a concept and a relation, return the cardinality of the corresponding role.Note that cardinality only exists if the min and max are the same.
(Nth-Domain Role-Cardinality 2 Relation) (Nth-Domain Role-Cardinality 1 Unary-Relation) (<=> (Role-Cardinality ?A ?B ?C) (And (Role-Min-Cardinality ?A ?B ?C) (Role-Max-Cardinality ?A ?B ?C)))