How to copy or add new class to Arma 2?

[McArcher 0]

I need a new building class, that will be a copy of Land_A_Hospital (hospital building) class, but I want to make it stronger. I think that this building is very weak in game (you can destroy it with a few shots of ZU-23). My questions are:

1) Is strength of building set up inside this class? (or how is it calculated?)

2) If, yes (strength can be changed), then how can I make my copy of this class and make it stronger ?

3) I also need a new class for special type of crate, that I want to be buyable with COIN. (COIN works with classes as i guess?) How to create new class?