Schemes populated after 2 passes through the Rules. g('4',B)? Yes(1) B='5' r(E,'3')? Yes(1) E='4' f(A,B)? Yes(2) A='1', B='2' A='4', B='3' g(A,B)? Yes(2) A='3', B='2' A='4', B='5' r(A,B)? Yes(3) A='1', B='2' A='3', B='5' A='4', B='3'