This is a question about the FT Fleet Book. What is the deal

This is a question about the FT Fleet Book. What is the deal with armor? How
much the stuff cost per mass point? This might sound like a dumb question but
I am new to the game and it is bugging the hell out of me to find out. I tried
to figure it out and depending on which ship model you look at it could be any
were from one point per mass to ten. they didnt do a very good job editing the
Fleet Book there are alot of mistakes in the ship designs. Still like it
though. If anyone can help that would be great. Andy.