Thanks for your email. If you are looking to attend USC, I do recommend you take the GMAT again. The reason is that your highest GMAT score is self-reported on your application, so admissions teams will focus on your best score. There isn't any harm to taking the exam again.
If you'd like, MBA.com provides 2 free GMAT exams. We also provide free GMAT advice here: http://www.stacyblackman.com/test-prep-hub/
, and we provide free 30 minute phone consultations here: http://www.stacyblackman.com/contact/
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