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: ~u. w <-> q_15. ~w. r_2 -> u.
~r_2 can be inferred via the modus tollens rule. ~u and ~w can be inferred via the conjunction rule. ~w and ~u can be inferred via the conjunction rule. w -> q_15 can be inferred via the biconditional elimination rule. q_15 -> w can be inferred via the biconditional elimination rule. ~q_15 can be inferred via the biconditional elimination rule.