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_8. p_8 <-> q_1. q -> q_1. q_1 -> q.
q <-> q_1 can be inferred via the biconditional introduction rule. q_1 <-> q can be inferred via the biconditional introduction rule. p_8 -> q_1 can be inferred via the biconditional elimination rule. q_1 -> p_8 can be inferred via the biconditional elimination rule. ~q_1 can be inferred via the biconditional elimination rule.