Consider the following premises. For all x_4, if x_4 were an astronaut, then x_4 is poor. There is at least one x_4 for which if x_4 were poor, then x_4 is a janitor. For all x_4, if x_4 were a janitor, then x_4 is an astronaut. Can we infer the following from them? There is at least one x_4 for which if x_4 were an astronaut, then x_4 is a janitor.
Yes.