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. p_6 -> s. s -> p_6. p_6 <-> t.
~p_6 can be inferred via the modus tollens rule. p_6 <-> s can be inferred via the biconditional introduction rule. s <-> p_6 can be inferred via the biconditional introduction rule. p_6 -> t can be inferred via the biconditional elimination rule. t -> p_6 can be inferred via the biconditional elimination rule.