Don leaves home at 2 pm

he drives 45 miles from his home in the first hour.

he stop for 90 minutes.

he then drives home at an average speed of 15. MP

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?