Problem 25 (2003 AMC 8)

In the figure, the area of square $WXYZ$ is $25\text{ cm}^2$. The four smaller squares have sides $1\text{ cm}$ long, either parallel to or coinciding with the sides of the large square. In $\Delta ABC$, $AB=AC$ and when $\Delta ABC$ is folded over side $BC$, point $A$ coincides with $O$, the center of square $WXYZ$. What is the area of $\Delta ABC$, in square centimeters? [See figure in original PDF]