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: p_12. q <-> q_9. p_12 -> u. ~q.
u can be inferred via the modus ponens rule. p_12 and ~q can be inferred via the conjunction rule. ~q and p_12 can be inferred via the conjunction rule. q -> q_9 can be inferred via the biconditional elimination rule. q_9 -> q can be inferred via the biconditional elimination rule. ~q_9 can be inferred via the biconditional elimination rule.