Check the picture below.
so let's add all sides and that'd be the area of the rectangular prism.
[tex]\stackrel{\textit{top and bottom}}{2(4\cdot 7)}+\stackrel{\textit{left and right}}{2(4\cdot 4)}+\stackrel{\textit{front and back}}{2(4\cdot 7)}\implies 56+32+56\implies 144[/tex]
