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: ~r_11. p_18 <-> q_4. p_18 <-> q_18. q_18 -> r_11.
~q_18 can be inferred via the modus tollens rule. p_18 -> q_4 can be inferred via the biconditional elimination rule. p_18 -> q_18 can be inferred via the biconditional elimination rule. q_4 -> p_18 can be inferred via the biconditional elimination rule. q_18 -> p_18 can be inferred via the biconditional elimination rule.