Well, I don't know anything about majors, but couldn't you major in structural, civil, or mechanical engineering? There are many aspects that go into the design of a coaster, including the basic design, mechanics(brakes, chain lift), and architectural drawing. If you work at a company would you do all of these things, or only one?
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Please disregard anything said by me that is incomprehensible, incoherent, or just dumb. I am and will be drained from the arduous school year, thank you!