Later, the incision direction of each piece was not explained, and it could only be thought according to customary thinking.

How can it be "big and small"? Shouldn't they all be the same size

Therefore, the surface area of each block is 2 [(10/3) (10/4)+(10/4) (10/5)+(10/5).

So the total surface area is 2400 square centimeters.