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 <-> q_2. ~s. r_4 or s_1. r_4 -> q_2.
s -> q_2 can be inferred via the biconditional elimination rule. q_2 -> s can be inferred via the biconditional elimination rule. ~q_2 can be inferred via the biconditional elimination rule.