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_9 or s. s <-> t_1. ~p_9.
s can be inferred via the disjunctive syllogism rule. s -> t_1 can be inferred via the biconditional elimination rule. t_1 -> s can be inferred via the biconditional elimination rule.