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: r_4 <-> p_8. q_8 -> r_4. p_8 -> q_8.
p_8 -> r_4 can be inferred via the transitivity rule. r_4 -> p_8 can be inferred via the biconditional elimination rule. p_8 -> r_4 can be inferred via the biconditional elimination rule.