Exercise 1. A batch of 400 containers for frozen orange juice contains 4 that are defective. Two are selected, at random, without replacement from the batch.
(1) What is the probability that the second one selected is defective given that the first one was defective?
(2) What is the probability that both are defective?
(3) What is the probability that both are non-defective?

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?