From what I have study about Function Point (one of my teacher was highly involved in the process of the theory of function point) and he wasn't able to answer all our answers.Function point fail in many way because it's not because you have something read or write that you can evaluate correctly. You might have a result of 450 functions points and some of these function point will take 1 hour ans some will take 1 weeks. It's a metric that I will never use again.