What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? r_1 -> q_8. q_8 -> r_1. q_8 -> r_1. ~r_1.
~q_8. ~q_8. r_1 <-> q_8. r_1 <-> q_8. q_8 <-> r_1. q_8 <-> r_1.