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_2 or p_12. p_12 <-> p_4. u_2 -> p_4. s.
p_12 -> p_4 can be inferred via the biconditional elimination rule. p_4 -> p_12 can be inferred via the biconditional elimination rule.