You got 44-47 for Quant on
MGMAT CATs and got a 39 on the GMAT???
RETAKE!!!!
39 Means your fundamentals are weak. Practice using the question banks posted by other forum members. There are questions categorized by topic (geometry, algebra, ratio, rates etc...). You should know what you are weak at and practice till you can solve 600-700 level qtns flawlessly and quickly (preferably within a min to 75s). With just solid fundamentals, you can easily break past Q45 and with your high verbal, you stand a big chance of breaking 700. Just make sure your GMATprep 2 indicates 700. YOU DO NOT WANT A WORSE 2nd SCORE.
Good luck!