What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? r_3 -> p_7. p_15 and s_1. p_7 -> ~p_15. r_3 -> p. p -> r_3.
r_3 -> ~p_15. p -> p_7. p_15. s_1. r_3 <-> p. p <-> r_3.