What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? p_9 <-> q_13. q_4 <-> p_9. ~w_2. w_2 <-> q_13. q_4 <-> s_2.
p_9 -> q_13. q_4 -> p_9. w_2 -> q_13. q_4 -> s_2. q_13 -> p_9. p_9 -> q_4. q_13 -> w_2. s_2 -> q_4. ~q_13.