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 <-> p. ~p. p_2 or s_4.
~s_4 -> p_2 can be inferred via the rewriting rule. s_4 -> p can be inferred via the biconditional elimination rule. p -> s_4 can be inferred via the biconditional elimination rule. ~s_4 can be inferred via the biconditional elimination rule.