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 or r_1. ~p. t -> p. r_1 <-> t.
~t can be inferred via the modus tollens rule. ~r_1 -> w can be inferred via the rewriting rule. r_1 -> t can be inferred via the biconditional elimination rule. t -> r_1 can be inferred via the biconditional elimination rule.