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 and r_4. ~s. s <-> p_1.
u_2 can be inferred via the simplification rule. r_4 can be inferred via the simplification rule. s -> p_1 can be inferred via the biconditional elimination rule. p_1 -> s can be inferred via the biconditional elimination rule. ~p_1 can be inferred via the biconditional elimination rule.