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. s_4 -> p. p -> q_8. q_8 -> s_4. u <-> s_4.
s_4 -> q_8 can be inferred via the transitivity rule. p -> s_4 can be inferred via the transitivity rule. q_8 -> p can be inferred via the transitivity rule. u -> s_4 can be inferred via the biconditional elimination rule. s_4 -> u can be inferred via the biconditional elimination rule. ~s_4 can be inferred via the biconditional elimination rule.