Given:
length(l)=20
width(w)=24
height(h)=12
Surface area of the box:
[tex]SA=2\times l\times w\text{ + 2}\times w\times h\text{ + 2}\times h\times l[/tex][tex]SA=2\times20\times24+2\times24\times12+2\times12\times20[/tex][tex]SA=960+576+480[/tex][tex]SA=2016in^2[/tex]