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: t -> ~q_8. p_4 <-> ~t. q_8.
~t can be inferred via the modus tollens rule. p_4 -> ~t can be inferred via the biconditional elimination rule. ~t -> p_4 can be inferred via the biconditional elimination rule.