What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y, y will listen to a song if and only if y will write a letter. There is at least one y for which if y writes a letter, then y is listening to a song.
For all y, if y listens to a song, then y is writing a letter. For all y, if y writes a letter, then y is listening to a song.