Check the picture below.
so let's simply get the area of each of those six rectangles and sum them up.
[tex]\stackrel{\textit{\large Areas}}{\stackrel{\textit{left and right}}{2(2\cdot 4)}+\stackrel{\textit{front and back}}{2(5\cdot 2)}+\stackrel{\textit{top and bottom}}{2(5\cdot 4)}}\implies 16+20+40\implies 76[/tex]
