I'm current studying RSL Music Theory grades and I'm stuck on a grade 6 question.

The question asks to write out two enharmonic equivalent notes to the note provided using sharps, flats, double-sharps and double-flats. The given stave does not show a key signature. 

I got through all of the questions fairly easily with the exception of one in which the given note is Ab. Obviously G# is an enharmonic but I'm struggling to think of a second enharmonic??

The only other notes either side would be "B flat, double-flat" or "F sharp double-sharp" - given that the stave in the question doesn't show a key signature, I'm not sure that this is possible?

any ideas?