2 wheels in the rear of nissan sentra will not move.

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the tires in the rear end of my nissan sentra will not move. someone left the handbreak up, but after i put it down, the 2 back wheels would not move. The front wheels are working, but the 2 back wheels would not roll at all. my sentra is a front 2 wheel drive. please help. i need to know what the problem might be, and also an estimate of repair. i am a female, and mechanics are ripping me off.