What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? p_13 <-> r_4. ~r_4. p_13 <-> r_1. p_4.
~r_4 and p_4. p_4 and ~r_4. p_13 -> r_4. p_13 -> r_1. r_4 -> p_13. r_1 -> p_13. ~p_13.