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: u -> q_3. u_3 -> u. u_3 <-> s.
u_3 -> q_3 can be inferred via the transitivity rule. u_3 -> s can be inferred via the biconditional elimination rule. s -> u_3 can be inferred via the biconditional elimination rule.