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 <-> r_4. t -> q_2. r_4 <-> q_16. q_2 -> t. ~q_16.
t <-> q_2 can be inferred via the biconditional introduction rule. q_2 <-> t can be inferred via the biconditional introduction rule. t -> r_4 can be inferred via the biconditional elimination rule. r_4 -> q_16 can be inferred via the biconditional elimination rule. r_4 -> t can be inferred via the biconditional elimination rule. q_16 -> r_4 can be inferred via the biconditional elimination rule. ~r_4 can be inferred via the biconditional elimination rule.