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 <-> r_1. s -> q. p_8 -> s. q -> p_8. ~r_1.
s -> p_8 can be inferred via the transitivity rule. p_8 -> q can be inferred via the transitivity rule. q -> s can be inferred via the transitivity rule. p_8 -> r_1 can be inferred via the biconditional elimination rule. r_1 -> p_8 can be inferred via the biconditional elimination rule. ~p_8 can be inferred via the biconditional elimination rule.