List Monad in F#

Now, it is time look some useful monads than Identity Monad. If you look LINQ query , you can’t miss it recognize the Bind operator(>>=) of a Monad:
public static IEnumerable SelectMany

I am using ResizeArray<_> as List, which is synonym for .Net generic list List<>. I have implemented standard Customer Order scenario to check monads Axioms:
( http://www.paul-abraham.com/MonadsInFSharp.doc)