1. You have to tell us a little bit more about this box: What do you cut where? Which shape has the box? Has the box a lid?

2. The volume never can't be 30 cm - that's a length.

What kind of pyramid are you referring to? Right pyramid? With a rectangle or triangle or 27-gon as base area? Tell us a little bit more please.

Best would be if you can type theoriginaltext of your problem...