In a large city, 15,000 workers lost their jobs last year. Of them, 7400 lost their jobs because their companies closed down or moved, 4600 lost their jobs due to insufficient work, and the remainder lost their jobs because their positions were abolished. If one of these 15,000 workers is selected at random, find the probability that this worker lost his or her job
a. because the company closed down or moved
b. due to insufficient work
c. because the position was abolished
Do these probabilities add up to 1.0? If so, why?