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_4 -> t. p_18 or r_4. ~p_18 or r_18. t -> r_18. r_18 -> t.
r_4 -> r_18 can be inferred via the transitivity rule. r_4 or r_18 can be inferred via the resolution rule. t <-> r_18 can be inferred via the biconditional introduction rule. r_18 <-> t can be inferred via the biconditional introduction rule.