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_13. p_13 <-> r_4. p_8 <-> q_8. q_8 -> r_4.
p_13 -> r_4 can be inferred via the biconditional elimination rule. p_8 -> q_8 can be inferred via the biconditional elimination rule. r_4 -> p_13 can be inferred via the biconditional elimination rule. q_8 -> p_8 can be inferred via the biconditional elimination rule. ~r_4 can be inferred via the biconditional elimination rule.