max:   4000 material + 3300 labor + 400 contract + 1000 delivery;
                                 
f1:       3 material +    2 labor                +      delivery <= 15;
f2:       6 material +    5 labor                +      delivery <=  7;
f3:       5 material +    4 labor +     contract +      delivery <=  9;
f4:       4 material +    3 labor                +      delivery <= 10;

	-inf < material <= 0;
	-inf < labor <= 0;
//	0 <= contract < +inf;
	-inf < delivery < +inf;