Step 1:
\The double integral is
and region is
.
Volume of the solid :
\If
, then the volume
of the solid that lies above the rectangle
and below the surface
is
.
Therefore the double integral
represents volume of the solid, below the surface
and above the rectangle
.
From the definition of double integrals, 

.
Solution :
\The double integral
represents volume of the solid.
.