Djspuddy, you have never mentioned the class name or title. It sounds like a business class to me. Personally, I think your instructor/professor doesn't care whether you can actually build a bike for a profit. I think he/she wants to know if you have the mental tools to understand what it takes to put together a business plan. Some of these tools should have been part of the curriculum taught in class. Other mental tools would be whether you can expand on something learned in class, or whether you can apply a basic principle to new ideas. That's what University is all about.
It's not the answer that is important, it is the "work shown" as to how you arrived at that answer that counts.
And I know I don't really want to teach you how to do this because you will never learn anything if others do it for you.