Question 3 Consider the definition of binary trees given in the lectures [25 credits] Tree Induction data Tree a Nul | Node (Tree a) a (Tree a) and the following three functions: f Tree a- Int f (Node Nul x Nul) 1 f (Node 1 x r ) (f 1) + (f r) gTree a -> Int hInt -> Tree a -> Int h acc Nulacc h acc (Node Nul x Nul)acc 1 h acc (Node xr h (h acc 1) r- H3 -HI Establish, using structua induction, that f t g t for all trees t of type Tree a. State clearly what property P is being proved by induction, including any quantifiers needed in the statement of P and in the inductive hypothesis