Hi Senthil,
Thanks for writing in. My expertise is in the admissions process, not the test itself, so I can't give you good insight on which courses might help you (there are other boards on this site for that though!). Traditionally, most business schools only look at your highest score, regardless of attempts, so a third attempt won't go against you on principle.
While I'm not sure what type of school you are targeting, there are plenty of programs that are available to you with a 660, so don't give up on just yet!
Best of luck!
Daniel Richards
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