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_5 for which x_5 is a janitor if and only if x_5 is a musician. For all x_5, x_5 is a musician or x_5 is rich. For all x_5, if x_5 were rich, then x_5 is a janitor.
There is at least one x_5 for which if x_5 were a janitor, then x_5 is a musician can be inferred via the existential biconditional elimination rule. There is at least one x_5 for which if x_5 were a musician, then x_5 is a janitor can be inferred via the existential biconditional elimination rule.