CAB, like most people.
C - Because LA is completely unseen, I find writing an essay from scratch is more difficult than using past knowledge to formulate a response. This is why I want to do this first because my brain is at it's freshest...
A - I find this requires a fair bit of thought to actually dissect the topic well and structure your essay appropriately. While this does use past knowledge, you still have to be able to think clearly to come up with a decent piece of writing.
B - I have a template piece, so most of the work is already done. My brain can be completely fried at this point and it won't matter as much because I don't have to be thinking of a whole new piece - I just need to tweak my memorised piece a little bit. This section, for me, requires the least thought so that's why I do it when all my brain power has gone...