Question 761479
surface Area of a rectangular prism 
= 2(width*height+length*width+length*height)
I will assume Height = 8mm
              Length = 7mm
              Width = 4mm
= 2(4*8 + 7*4 + 7*8)
=2( 32 + 28 + 56)
=2(116)
=232mm^2
Hope this helps.
:-)