What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If John listens to a song, then it is sunny. Linda is writing a letter or Sarah is not sleeping. John is listening to a song if and only if Linda is writing a letter.
If Sarah sleeps, then Linda is writing a letter. If John listens to a song, then Linda is writing a letter. If Linda writes a letter, then John is listening to a song.