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: ~q. p <-> q. p or ~s. s or ~p.
s -> p can be inferred via the rewriting rule. p -> s can be inferred via the rewriting rule. p -> q can be inferred via the biconditional elimination rule. q -> p can be inferred via the biconditional elimination rule. ~p can be inferred via the biconditional elimination rule.