In the Grand Prix example with varying tax rates, the optimal solution more than satisfies customer demands. Modify the model so that regions have not only lower limits on the amounts they require, but upper limits on the amounts they can sell. Assume these upper limits are 50 autos above the required lower limits. For example, the lower and upper limits for region 1 are 450 and 500.

Modify the model and find the optimal solution. How does it differ from the solution without upper limits?