Consider the following premises. For all x_6, x_6 is an electrician or x_6 is not a janitor. For all x_6, x_6 is a janitor if and only if x_6 is rich. For all x_6, x_6 is not an electrician. Can we infer the following from them? If we can, name the inference rule being used: For all x_6, x_6 is not rich.
 From the fact that for all x_6, x_6 is an electrician or x_6 is not a janitor we can infer that for all x_6, if x_6 were a janitor, then x_6 is an electrician via universal rewriting. From the fact that for all x_6, if x_6 were a janitor, then x_6 is an electrician, and that for all x_6, x_6 is not an electrician we can infer that for all x_6, x_6 is not a janitor via universal modus tollens. Finally, from the fact that for all x_6, x_6 is a janitor if and only if x_6 is rich, and that for all x_6, x_6 is not a janitor we can infer that for all x_6, x_6 is not rich via universal biconditional elimination. Therefore, the answer is yes.