The example I did in class is available online. I strongly recommend using this when doing your quiz .
This is the link
Note: I remind you on the example, but I will do so again. The example starts from scratch. That is, I give you hours work and then we see what each country (in the example person) can produce. Then I calculate the comparative advantage. On the quiz, however, I already give you the production possibilities. Then I ask you to calculate comparative advantage. Thus I have saved you a step and you can just go right towards solving for who has a comparative advantage in what.