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: s_3 <-> q_4. t_4 -> s_3. s_3 -> t_4.
t_4 <-> s_3 can be inferred via the biconditional introduction rule. s_3 <-> t_4 can be inferred via the biconditional introduction rule. s_3 -> q_4 can be inferred via the biconditional elimination rule. q_4 -> s_3 can be inferred via the biconditional elimination rule.