The Prenucleolus: 

x1 = 3.5
x2 = 3.5
x3 = 3.5
x4 = 3.5

Excesses:

0 ()
-8.88178e-16 (1 3 )
-1e-06 (2 4 )
-1e-06 (1 2 3 4 )
-3.5 (3 )
-3.5 (1 )
-3.5 (4 )
-3.5 (1 3 4 )
-3.5 (2 )
-3.5 (2 3 4 )
-3.5 (1 2 4 )
-3.5 (1 2 3 )
-4 (1 2 )
-7 (1 4 )
-7 (3 4 )
-7 (2 3 )