Split a rectangle
As Pieter Torbijn fooled us with our last contest (he was right though) this new contest came alive.
Start with a set of pentominoes :

Place a pentomino in each corner of a rectangle.
The length and width of the rectangle may at most be 16 units long.
Then place the other pentominoes in such a way, that every pentomino borders at least one other pentomino by the length of at least one unit.
All pentominoes must fit completely inside the rectangle; also each one of them must cover just 5 unit squares on the grid.
There must be just 2 empty areas of equal size.
Your challenge is to maximise these two areas.
In our example, both areas contain 66 unit squares.

This Excel file will make searching for a solution a bit easier.
To download it click with the right mouse button and choose �Save target as ...� to save this Excel file on your hard disk or diskette.

An help in searching for solutions is the program �FlatPoly2�. You can download it from the homepage of Aad van de Wetering, Driebruggen.