What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? exists x_15: P_15(x_15) -> Q_15(x_15). forall x_15: Q_15(x_15) -> S_1(x_15). forall x_15: P_15(x_15). forall x_15: Q(x_15) <-> S_1(x_15).
exists x_15: Q_15(x_15). exists x_15: P_15(x_15) -> S_1(x_15). forall x_15: Q(x_15) -> S_1(x_15). forall x_15: S_1(x_15) -> Q(x_15).