I tend to do C then A then B, mainly because I tend to take the least on C, so I do it first to gauge how much time I have remaining to transfer over to the other two, and also because it's fresh in my head etc as others have mentioned. Then I do A next because that's the one I have to ensure I fit all my points in for, so if I do happen to go massively overtime (i.e. use up my hour PLUS any additional time I gained from finishing C early), then I can just write less in context since getting in all my points isn't as vital as it is in A (in my opinion anyway). But of course, this plan is according to the strategies and lengths I wrote at, which obviously will vary between people.