How to get a class to support duplexing?

[Steve Gaarder]

I have two printers, and HP4200 and HP4300, that I combined into a class.  Both printers have duplexers, but when I try to print to the class, the applications (e.g. Firefox) do not know that the printers can do duplexing.  Any ideas on how to fix this?

thanks,

Steve Gaarder