4/0, 4/1, 4/4

I don't think I've heard 4/0, 4/1, or 4/4 on a bussiness card before. I knew it had something to do with colors though because of CYMK mood.
I learned that 4/0 means that there are 4 colors on the front and 0 colors on the back
                    4/1 means that there are 4 colors on the front and 1 color on the back
                    4/4 means that there are 4 colors on the front and 4 colors on the back.

The cheapest one is the 4/0. The more colors you have on both the front and back of the card, the more expenisve it will be. For my denwa business card, I will use the 4/0 colors.

4/4

 4/4

 I think this is a 4/1
 4/0