It depends on how much time you spend on it each day.
Step 1: Work on understanding the case study and get going on your high level architecture for a couple of hours each day for a week.
Step 2: Take one or two days off and go drink a few pints with a midget and ride your unicycle around town.
Step 3: Re-visit the problem and your solution and work on it for a couple of hours every day for another couple of weeks.
Step 4: Go to Step 2
Step 5: Pull an "all-nighter" and revise most of your solution radically and then submit it
Step 6: Take Part 3 without preparing for it at all - perhaps even a pint or two before taking it will most likely help.
Step 7: Get back on your unicycle and meet the midget again at a pub and get all messed up.
Step 8: Ask your boss for a raise because you received your
SCEA certificate and because you rode your unicycle into a small roadside stand that sells glass menageries and destroyed $1,750 worth of little Elmo figurines.
All in all, you'll spend around 40-50 hours on it. Any less and you may be too smart for the rest of us, you cheated or your documentation/presentation stinks. Any more and
you should probably think about getting a job at a glass menagerie stand with guard rails around it to protect yourself from drunk SCEAs on their unicycles.