What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? q_11 <-> q_2. ~s. q_11 -> s. s -> q_11. q_2 or ~r_1.
~q_11. r_1 -> q_2. q_11 <-> s. s <-> q_11. q_11 -> q_2. q_2 -> q_11.