Example. We have four boxes. Box 1 contains 2000 components of which 5 percent are defective. Box 2 contains 500 components of which 40 percent are defective. Boxes 3 and 4 contain 1000 each with 10 percent defective. We select at random one of the boxes and we remove at random a single component. What is the probability that the selected component is defective? The space of this experiment consists of 4000 good (g) components and 500 defective (d) components arranged as follows.

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