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: ~s_4. s_4 <-> p. p <-> q_9.
s_4 -> p can be inferred via the biconditional elimination rule. p -> q_9 can be inferred via the biconditional elimination rule. p -> s_4 can be inferred via the biconditional elimination rule. q_9 -> p can be inferred via the biconditional elimination rule. ~p can be inferred via the biconditional elimination rule.