I think we are supposed to arrive at a solution that does not need OOP. That said, if you have working code that uses OOP and can't figure out where to go with it, submit what you have and the nitpicks will guide you in the right direction.
Most likely you will end up removing the OOP for 4b, though (I think).
Okay, somebody else say something now before I ramble on indefinitely!
[edited for spelling] [ March 11, 2007: Message edited by: Katrina Owen ]