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_1 -> p_3. p_3 <-> p_4. p_4 -> q_1.
p_4 -> p_3 can be inferred via the transitivity rule. p_3 -> p_4 can be inferred via the biconditional elimination rule. p_4 -> p_3 can be inferred via the biconditional elimination rule.