2013 Gauss 8 Problem 23

Greg, Charlize, and Azarah run at different but constant speeds. Each pair ran a race on a track that measured 100 m from start to finish. In the first race, when Azarah crossed the finish line, Charlize was 20 m behind. In the second race, when Charlize crossed the finish line, Greg was 10 m behind. In the third race, when Azarah crossed the finish line, how many metres was Greg behind?

\textbf{(A)}\ 20\quad \textbf{(B)}\ 25\quad \textbf{(C)}\ 28\quad \textbf{(D)}\ 32\quad \textbf{(E)}\ 40

If there are no answer choices shown, enter a numerical answer.

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