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_4 <-> q. q_1 -> q. p_4 -> q_1.
p_4 -> q can be inferred via the transitivity rule. p_4 -> q can be inferred via the biconditional elimination rule. q -> p_4 can be inferred via the biconditional elimination rule.