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_2 <-> q_4. p_8 <-> t_2. q_4 or p_8.
t_2 -> q_4 can be inferred via the biconditional elimination rule. p_8 -> t_2 can be inferred via the biconditional elimination rule. q_4 -> t_2 can be inferred via the biconditional elimination rule. t_2 -> p_8 can be inferred via the biconditional elimination rule.