What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? r_1 -> p_11. p_11 -> r_1. ~q_11. p_11 <-> q_11.
r_1 <-> p_11. p_11 <-> r_1. p_11 -> q_11. q_11 -> p_11. ~p_11.