Year 12s: what will be the first way you research your future options? >>

Differentiation open box help?

bigger pic

Attachment not found

Apparently the formula i have to use are
l+4h+24=648
and
b+4h+24=458

I am just unsure how you get these. If i open up the box then shouldn't it be
l+2h+24 and b+2h+24.

It's the 4h that is really throwing me off, i know there are two folds on every side, but if i fold it up shouldn't both of the folds in the second drawing add up to the h value from the first?

Sorry if i am being idiotic just lost how they got +4h in the formulas