Yes that's exactly what you have to do! As you said the treble clef with the eight below it does read an octave below, so you can easily write it in bass clef. On one stave (treble clef) you'll have the two treble parts, and the second stave (bass clef) the treble an octave lower with stems facing up, and the bass clef with stems facing down. Hope this confirms what you said. Good luck with your exam, i'm sure it will be fine.