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_6 -> p_8. ~q_6. p_8 -> q_6. q_8 -> p_8. p_8 -> q_8.
~p_8 can be inferred via the modus tollens rule. q_6 -> q_8 can be inferred via the transitivity rule. q_8 -> q_6 can be inferred via the transitivity rule. q_6 <-> p_8 can be inferred via the biconditional introduction rule. p_8 <-> q_6 can be inferred via the biconditional introduction rule. q_8 <-> p_8 can be inferred via the biconditional introduction rule. p_8 <-> q_8 can be inferred via the biconditional introduction rule.