CEMC Hypatia, 2008

Geometry Difficulty 2.0 Junior Prove it Canada

In the diagram, $ABCD$ is a trapezoid with $AD$ parallel to $BC$ and $BC$ perpendicular to $AB$ . Also, $AD = 6$ , $AB = 20$ , and $BC = 30$ . Determine the area of trapezoid $ABCD$ .

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