What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_20: T_3(x_20). forall x_20: P_20(x_20) -> R_20(x_20). exists x_20: P_20(x_20) or Q_20(x_20). forall x_20: Q_20(x_20) -> R_20(x_20).
exists x_20: R_20(x_20).