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_3. p_15 <-> u. u.
p_3 and u can be inferred via the conjunction rule. u and p_3 can be inferred via the conjunction rule. p_15 -> u can be inferred via the biconditional elimination rule. u -> p_15 can be inferred via the biconditional elimination rule.