What is the surface area formula of a 3-dimensional rectangle?

##SA=2(wl+lh+hw)##
For a rectangular prism with sides ##wlh## the surface area is
##SA=2(wl+lh+hw)##
This occurs since there are two pairs of three different faces on every rectangular prism.
Each pair of faces is a different rectangle using two of the the three dimensions of the prism as its own side.
One side is just ##wl## another is just ##lh## and the other ##hw##. Since there are two of each that is reflected in the formula by the multiplication by ##2##.
This could also be imagined as a series of flattened-out rectangles:
The blue rectangles are ##2*wl##.
The yellow rectangles are ##2*lh##.
The red rectangles are ##2*hw##.
Again the surface area would be
##SA=2wl+2lh+2hw##
##=2(wl+lh+hw)##