What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_4, x_4 is a mechanic. For all x_4, x_4 will listen to a song or x_4 is not a mechanic. There is at least one x_4 for which if x_4 were a janitor, then x_4 is listening to a song.
For all x_4, if x_4 were a mechanic, then x_4 is listening to a song.