What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: ~q_15 or p. p_9 -> q_15. p_15 <-> q_15. p_9 or p_15.
p_15 -> q_15 can be inferred via the biconditional elimination rule. q_15 -> p_15 can be inferred via the biconditional elimination rule.