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 -> q_4. ~r_3. r_3 <-> t. q_4 -> t.
t <-> q_4 can be inferred via the biconditional introduction rule. q_4 <-> t can be inferred via the biconditional introduction rule. r_3 -> t can be inferred via the biconditional elimination rule. t -> r_3 can be inferred via the biconditional elimination rule. ~t can be inferred via the biconditional elimination rule.