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 -> p. ~p. p -> t. s.
~t can be inferred via the modus tollens rule. ~p and s can be inferred via the conjunction rule. s and ~p can be inferred via the conjunction rule. t <-> p can be inferred via the biconditional introduction rule. p <-> t can be inferred via the biconditional introduction rule.