Cliché galore Alert!
a) It depends on where you start from. Take a practice test & see what your current score is; take it from there. Obviously, if you are starting from 600 you would need some time to build up the basics, before you move on to the real test. At the same time, you might be scoring 720 right now, which would mean you have the basics covered & 750 is not that far off. How much time you would need in these scenarios is something that neither you nor anyone else can forecast. It will come to you once you start, review your progress & make changes accordingly.
b) It depends on how much 'uninterrupted' time you can take out in those months. It took me 3 weeks to raise my score from 750 to 780, but I had the advantage of being able to take out 4-5 continuous hours each day. Understand your work/life commitments before structuring a study plan.
Good luck, start today!
