Is it an H ?  Is it an X ?  It's the rectangle corners pentomino problem
You get one set of pentominoes :

Occupy all four corners of a rectangle with pentominoes.
Neighbouring pentominoes should share at least one side.
All pentominoes should lie inside the rectangular surface.
Two areas enclosed by the pentominoes and the edge of the rectangle should have equal sizes.
Your challenge is to maximise these two areas.
In our example the area is 98.

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.