1. Of 600 car parts produced, it is known that 350 are produced in one plant, 150 parts in a second plant, and 100 parts in a third plant. Also it is known that the probabilities are 0.15, 0.2, and 0.25 that the parts will be defective if they are produced in the ?rst, second, or third plants, respectively. What is the probability that a randomly picked part from this batch is not defective?

2. One class contains 5 girls and 10 boys and a second class contains 13 boys and 12 girls. A student is randomly picked from the second class and transferred to the ?rst one. After that, a student is randomly chosen from the ?rst class. What is the probability that this student is a boy?