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 or ~q_18. q_3 <-> q_18. r_4 -> r_1. p -> q_3.
q_18 -> r_4 can be inferred via the rewriting rule. q_3 -> q_18 can be inferred via the biconditional elimination rule. q_18 -> q_3 can be inferred via the biconditional elimination rule.