Answer :
Maybe something like in attachment?
Where side length of big cube is 9 units and side length of that missing small cube is 1 unit.
So total volume is 728 cubic units.
Where side length of big cube is 9 units and side length of that missing small cube is 1 unit.
So total volume is 728 cubic units.
![View image geerky42](https://us-static.z-dn.net/files/d10/77f175047ccfc0bd8e907a4f18a7c9f2.jpg)