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: p_1 -> q. q_3 -> p_1. s_3 <-> q.
q_3 -> q can be inferred via the transitivity rule. s_3 -> q can be inferred via the biconditional elimination rule. q -> s_3 can be inferred via the biconditional elimination rule.