The dimensions of the box are 6 by 4 by 20.
To find the surface area of the box, multiply 6 by 4, 4 by 20, and 20 by 6.
The answers for those is 24, 80, and 120.
Add those all together to get 224.
Then, multiply that by 2 since 224 is only half of the surface area.
The answer is actually 448 square inches, not 512.
Hope this helps!
