Consider the following premises. forall y: R(y) -> ~Q(y). S(i) <-> u_4. forall y: Q(y). forall y: S(y) <-> R(y). Can we infer u_4 from them?
 From forall y: R(y) -> ~Q(y), forall y: Q(y) we can infer forall y: ~R(y). From forall y: S(y) <-> R(y), forall y: ~R(y) we can infer forall y: ~S(y). From forall y: ~S(y) we can infer ~S(i). Finally, from S(i) <-> u_4, ~S(i) we can infer ~u_4, which contradicts u_4. Therefore, the answer is no.