What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? s_2 -> p_15. s_2 <-> w_3. ~p_15. p_15 -> s_2.
~s_2. s_2 <-> p_15. p_15 <-> s_2. s_2 -> w_3. w_3 -> s_2.