What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_19: P_19(x_19) <-> Q_19(x_19). r <-> Q_19(a_15). P_19(a_15) -> r.
r -> Q_19(a_15). Q_19(a_15) -> r. forall x_19: P_19(x_19) -> Q_19(x_19). forall x_19: Q_19(x_19) -> P_19(x_19).