CPLEX 6.6.0: 
CPLEX 6.6.0: optimal solution; objective 110528000
6 simplex iterations (3 in phase I)
P :=
1 al      2200
1 steel   2800
2 al         0
2 steel   5000
3 al      4500
3 steel    500
4 al         0
4 steel   3000
;

I :=
0 al         0
0 steel      0
1 al      1200
1 steel    400
2 al         0
2 steel   3200
3 al      3100
3 steel   1000
4 al      1500
4 steel   1500
;