What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Robert is not a janitor. For all x_15, if x_15 plays squash, then x_15 is a janitor. Susan is listening to a song if and only if Robert is playing squash.
If Susan listens to a song, then Robert is playing squash. If Robert plays squash, then Susan is listening to a song.