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: ~p -> q. s -> ~q_11. s <-> p. q_11.
~s can be inferred via the modus tollens rule. s -> p can be inferred via the biconditional elimination rule. p -> s can be inferred via the biconditional elimination rule.