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_6 or r. p_6 -> q_2. r -> q_2. q_2 -> p_6.
r -> p_6 can be inferred via the transitivity rule. q_2 can be inferred via the disjunction elimination rule. p_6 <-> q_2 can be inferred via the biconditional introduction rule. q_2 <-> p_6 can be inferred via the biconditional introduction rule.