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: w <-> r_2. t_3 or w. ~q_15. t_3 -> q_15.
~t_3 can be inferred via the modus tollens rule. w -> r_2 can be inferred via the biconditional elimination rule. r_2 -> w can be inferred via the biconditional elimination rule.