This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
The essay exam just questions a few of your decisions you made during your assignment. So you just have to describe what you did and why you did it. You can't fail on this test in my opinion. You will only fail because your locking mechanism wasn't meeting the requirements for example.
Don't be afraid of the written exam: if you did the assignment on your own, this exam will be a piece of cake.