The University of Michigan shapes Ann Arbor's economy significantly. It employs about 30,000 workers, including about 12,000 in the medical center. Other employers are drawn to the area by the university's research and development money, and by its graduates. High tech, health services and biotechnology are other major components of the city's economy; numerous medical offices, laboratories, and associated companies are located in the city. Automobile manufacturers, such as General Motors and Visteon, also employ residents.
Try to answer this question if possible (otherwise reply "unanswerable"): Who are the automobile manufacturers that are the major components of the city's economy?
unanswerable