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: There is at least one x_4 for which if x_4 were a janitor, then x_4 is sleeping. For all x_4, x_4 will sleep. For all x_4, if x_4 sleeps, then x_4 is a janitor.
For all x_4, x_4 is a janitor can be inferred via the universal modus ponens rule. There is at least one x_4 for which x_4 is a janitor if and only if x_4 will sleep can be inferred via the existential biconditional introduction rule. There is at least one x_4 for which x_4 will sleep if and only if x_4 is a janitor can be inferred via the existential biconditional introduction rule.