What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall y_2: R(y_2) -> S_1(y_2). exists y_2: S_1(y_2) -> R(y_2).
exists y_2: S_1(y_2) <-> R(y_2). exists y_2: R(y_2) <-> S_1(y_2).