Answer to yesterday's was C.
DIFFICULTY: HARD
Thanks to in Mission 1400+ for this problem! A right rectangular prism has square bases with side length x inches and a height of 18 inches. A square tunnel with side length 4 inches is cut completely through the prism, perpendicular to the square bases. The tunnel is centered in each base. The total surface area of the remaining solid, including the interior walls of the tunnel, is 960 square inches. What is the volume, in cubic inches, of the remaining solid?