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: For all x_6, if x_6 were excited, then x_6 is working. For all x_6, x_6 will not drink water. For all x_6, if x_6 drinks water, then x_6 is excited. For all x_6, if x_6 works, then x_6 is drinking water. There is at least one x_6 for which x_6 is a janitor if and only if x_6 is excited.
For all x_6, x_6 will not work can be inferred via the universal modus tollens rule. For all x_6, if x_6 were excited, then x_6 is drinking water can be inferred via the universal transitivity rule. For all x_6, if x_6 drinks water, then x_6 is working can be inferred via the universal transitivity rule. For all x_6, if x_6 works, then x_6 is excited can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 were a janitor, then x_6 is excited can be inferred via the existential biconditional elimination rule. There is at least one x_6 for which if x_6 were excited, then x_6 is a janitor can be inferred via the existential biconditional elimination rule.