Hi

I did the 2 gmat preps and the free Manhattan without looking at any part of the material and I got:

Manh.
44 34
(19 inc. SC=10, RC=3, CR=6)
score 640
done under ok conditions

Prep Test 2
37 41
(9 inc. SC = 5, RC=3, CR=1)
score 680
done under optimal conditions

Prep 1
41 36
score 640
done under unfavorable conditions. Stopped halfway through. Did the verbal last night at 3 am with little care/concentration.

Math: on avg. I get wrong 1/3 in PS, 2/3 DS.
Verbal: SC clearly a problem.

I did the 15 practice questions for each section in gmat prep. Unfortunately didn't write the scores down, thought I'd be able to look back at them and the score, but I distinctly remember that I got smth like 5 out of 15 wrong in SC, CR I think I was perfect and got 1-2 wrong on RC. Math p.q. about 1-3 wrong each sec.

I have bought the OG. I have about 3 weeks to practice. 4-5 hours per day. The gmat score is very important as I might get full scholarship if I get a high enough score.

So is this doable?

Which books/material should I study?

What would be my optimal strategy to follow to achieve my goal? Do the whole OG? Just specific sections first? Only the harder questions? Do a practice test a week or just alot of them at the end...etc

Thanks