Consider the following premises. If Michael climbs a mountain, then John is taking a plane. For all x_6, if x_6 takes a plane, then x_6 is rich. For all x_6, if x_6 were rich, then x_6 is a janitor. Can we infer the following from them? If we can, name the inference rule being used: If Michael climbs a mountain, then John is a janitor.
 From the fact that for all x_6, if x_6 takes a plane, then x_6 is rich, and that for all x_6, if x_6 were rich, then x_6 is a janitor we can infer that for all x_6, if x_6 takes a plane, then x_6 is a janitor via universal transitivity. From the fact that for all x_6, if x_6 takes a plane, then x_6 is a janitor we can infer that if John takes a plane, then John is a janitor via universal instantiation. Finally, from the fact that if Michael climbs a mountain, then John is taking a plane, and that if John takes a plane, then John is a janitor we can infer that if Michael climbs a mountain, then John is a janitor via transitivity. Therefore, the answer is yes.