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: t_4 <-> t_2. t_2 -> s. ~s.
~t_2 can be inferred via the modus tollens rule. t_4 -> t_2 can be inferred via the biconditional elimination rule. t_2 -> t_4 can be inferred via the biconditional elimination rule.