Mathison and the cubic tree

After playing board games, buying letters, and shuffling decks, Mathison has finally decided to study. He opens his favorite book, CLRS, and decides to solve a graph problem. The problem is described below and you can find it by its number, 25.1-11, on page 693 (3rd edition only). You are given a tree with N nodes where each node has a value associated with it. Define PROD(u, v) to be the produc