3. Let T be any binary tree. Show that if x(v) is the preorder rank of v and y(v) is the depth of v, for all nodes v of T, then the resulting drawing of 1' has no edges crossing. 3. Let T be any binary tree. Show that if x(v) is the preorder rank of v and y(v) is the depth of v, for all nodes v of T, then the resulting drawing of 1' has no edges crossing