set F = the identity-preserving multiplicative antimultiplicative Functor of C,D;
take the identity-preserving multiplicative antimultiplicative Functor of C,D ; :: thesis: ( the identity-preserving multiplicative antimultiplicative Functor of C,D is covariant & the identity-preserving multiplicative antimultiplicative Functor of C,D is contravariant )
thus ( the identity-preserving multiplicative antimultiplicative Functor of C,D is covariant & the identity-preserving multiplicative antimultiplicative Functor of C,D is contravariant ) ; :: thesis: verum