The A-1 Corporation supplies airplane manufacturers with preformed sheet metal panels that are used on the exterior of aircraft. Manufacturing these panels requires only five sheet metal-forming machines, which cost $500 each, and workers. These workers can be hired on an as-needed basis in the labor market at $9,000 each. Given the simplicity of the manufacturing process, the preformed sheet metal panel market is highly competitive. Therefore, the market price for one of A-1's panels is $80. Based on the production data in the accompanying table, how many workers should A-1 hire to maximize its profits?

Machines Workers Output

5 0 0

5 1 600

5 2 1,000

5 3 1,290

5 4 1,480

5 5 1,600

5 6 1,680

What are some examples of using spot exchange?