Image data structure: An image(square image) can be stored as a tree: A node is white if the image is white, is black if the image is black, and is mixed if it contains both. White and black nodes are leaves, whereas a mixed node will have exactly 4 children, representing the 4 quadrants in the image. Given 2 images (trees), find the image representing their intersection. (Intersection: B^B -> B, B^W -> W, W^W->W)