Model, which mathematical formulation is as follows:
The intersection of feasible regions of both variables is unlimited. The iso-profit line can be shifted to the right with no limits. The optimal solution is unbounded. The only help in such a case is to add constrain, to find some limit or demand. This finding is very likely to be successful because no real process is without limit.
The feasible area for the first constrain was drawn using points A(0;1) and B(4;0) ,
for second constrain points C(0;2) and D(4;4).