What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? s_2 <-> q_15. ~q_15. u. s_2 <-> p.
~q_15 and u. u and ~q_15. s_2 -> q_15. s_2 -> p. q_15 -> s_2. p -> s_2. ~s_2.