Class Extension Problem Chapter 1

Page 14-15, trying to declare and set outlets for the Simple Question App. 2 errors I cannot get past.

on the line "@interface BNRQuizViewController () an error message pops up saying Cannot declare class extension for 'BNRQuizViewController

on the line "@implementation BNRQuizViewController an error message pops up saying Reimplementation of class ‘BNRQuizViewController’

I cannot link the buttons to the File Owner’s Placeholder because I cannot figure out what I did wrong. Everything has been typed in exactly as is shown in book. Triple checked to make sure.