set PRODUCTS = x1 x2 s1 s2 s3;
set RESOURCES = c1 c2 c3;

param price := x1 -1 x2 -4 s1 0 s2 0 s3 0;

param avail := c1 3 c2 5 c3 3;

param use :  x1 x2 s1 s2 s3  :=
   c1         2  2 -1  0  0
   c2        -1  2  0  1  0
   c3         3 -1  0  0  1
   ;