The Boards and Blades Company manufactures skateboards and in-line skates. The company can produce a maximum of 21 skateboards and pairs of in-line skates per day. It makes a profit of $20 on a skateboard and a profit of $15 on a pair of in-line skates. The company's planners want to make at least 2 skateboards but not more than 8 skateboards per day. To keep customers happy, they must make at least 3 pairs of in-line skates per day.

Determine the objective function