### Calculating the probability of an outcome

Two boxes of light bulbs are in a warehouse. Box 1 contains 95 good bulbs and 5 defective bulbs, while Box 2 contains 90 good and 10 defective bulbs. We choose one of these boxes at random and test 3 bulbs chosen at random from this box, without replacement. If all 3 bulbs are defective, what is the probability that we selected