multiply(identity(),X) -> X
multiply(inverse(X),X) -> identity()
multiply(multiply(X,Y),Z) -> multiply(X,multiply(Y,Z))
multiply(inverse(X),multiply(X,Y)) -> Y
multiply(X,identity()) -> X
inverse(identity()) -> identity()
inverse(inverse(X)) -> X
multiply(X,inverse(X)) -> identity()
multiply(X,multiply(inverse(X),Y)) -> Y
b() -> d()
inverse(multiply(X,Y)) -> multiply(inverse(Y),inverse(X))