Given that X ~ N(300, 15). We survey 20 at a time and are interested in the distribution of X-bar. Find the maximum value for the bottom quarter of the distribution for X-bar.

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?