2001 Gauss 7 Problem 16

BC is a diameter of the circle with centre O and radius 5, as shown. If A lies on the circle and AO is perpendicular to BC, the area of triangle ABC is

\textbf{(A)}\ 6.25\quad \textbf{(B)}\ 12.5\quad \textbf{(C)}\ 25\quad \textbf{(D)}\ 37.5\quad \textbf{(E)}\ 50

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

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