multiple choice option and payment

I am trying to setup options for product in Opencart but not getting it right.
For my printing website to buy a product - users have to chose size (say A3, a4 ..), side (single or double), quantity (100,200 ..so on) and as per selection final amount will be displayed.
I tried to create options on these three and make parent option between them but still cudn't get the desired output. Help please!

It may be less headache than that just to follow the Extensions button top right into the store and look for product options quantities -- or the like.