# Elementary Geometry

Geometry Level 2

In the above figure, $$O$$ is the center of circle. Angle $$AOB = 90^\circ$$. The line $$AC$$ is parallel to $$OD$$. $$OB$$'s length is equal to twenty centimeters. $$BD$$'s length is equal to four centimeters. Determine the length of $$AB$$.

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