SMO 2012 Junior Round 1 Question 26

In the diagram, $A,B(20,0)$ lie on the $x$-axis and $C(0,30)$ on the $y$-axis, with $\angle ACB=90^\circ$. A rectangle $DEFG$ is inscribed in $ABC$. Given $[CGF]=351$, calculate the area of $DEFG$.