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: q <-> s_2. p <-> q.
q -> s_2 can be inferred via the biconditional elimination rule. p -> q can be inferred via the biconditional elimination rule. s_2 -> q can be inferred via the biconditional elimination rule. q -> p can be inferred via the biconditional elimination rule.