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_10 -> q_14. r_1 <-> q_14. q_14 -> p_10. p. r_1 -> ~q_18. q_18.
~r_1 can be inferred via the modus tollens rule. p and q_18 can be inferred via the conjunction rule. q_18 and p can be inferred via the conjunction rule. p_10 <-> q_14 can be inferred via the biconditional introduction rule. q_14 <-> p_10 can be inferred via the biconditional introduction rule. r_1 -> q_14 can be inferred via the biconditional elimination rule. q_14 -> r_1 can be inferred via the biconditional elimination rule.