If you look at the speaker magnet, it might have the ohm rating on it. If the book says 2 or 4, then the speaker comes in 2 or 4 ohm ratings.
Here's a link that will help ya once you figure out the speaker rating:
http://www.the12volt.com/caraudio/wo...igurations.asp. Just choose 2 speakers, then your ohms and click the button to see all the ways it's possible to be wired.