Suppose each node v of a binary tree T is labeled with its value ∫ (v) in a level numbering of T. Design a fast method for determining  ∫ (u) for the lowest common ancestor (LCA), u, of two nodes v and w in T, given  ∫ (v) and  ∫ (w). You do not need to find node u, just compute its level numbering label.