Person A leaves his home to visit his cousin, person B, who lives 274 miles away. He travels at an average rate of 52 miles per hour. One half-hour later, person B leaves her house to visit person A, traveling at an average rate of 72 miles per hour. How long after person B leaves will it be before they meet

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?