Please visit the Course Work>Exercises>Week 7 section for review exercises on preference relations.
For completeness, I've added some supplementary material about trees in the Week 1 Lectures section.
Please use the forum to identify topics you'd like to review in the second part of the class in week 12. This part will be student-driven. The more notice I have the better I'll be able to prepare to help you prepare for the exam.