1. In fact, if you add four original cubes, then 8X8X4=256 square centimeters.

2. Two parts are added, so it is 1X 1X2=2 square decimeters.

3. The reduction of surface area is the perimeter of the bottom multiplied by the reduced height.

So the base perimeter =48/2=24, and the side length =24/4=6.

Volume =6X6X(6+2)=288 cubic centimeters.