Please help with 6 and 8, and explain if possible

6. (2 points) Show that for any leaf v in a binary search tree, if u is the parent of v, then either key[v] is the largest key irn the tree smaller than key[u], or key[v] is the smallest key in the tree larger than key[u]. (Heileman, p.216) 7. (2 points) Prove that the maximum number of nodes in a binary tree of height h is 21 8. (1 point) In terms of M and L, what is the maximum height of a BTree with n elements