Friday HW

I gave different classes different numbers, but if you've forgotten or want to do these instead:
There is a pattern formed starting with one box (perimeter=4) then two boxes next to each other (perimeter=6) then three next to each other, four next to each other, etc. What will the perimeter of the 12th box be? Can you figure out a formula that you could use to find the perimeter of any size rectangle?