Decide whether each of the following are frictional, structural, or cyclical unemployment:
a. The economy gets worse, so General Motors shuts down a factory for four months, laying off workers.
b. General Motors lays off 5,000 workers and replaces them with robots. The workers start looking for jobs outside the auto industry.
c. About 10 workers per month at a General Motors plant quit their jobs because they want to live in another town. They start searching for work in the new town.