The city subway is being extended to include a new stop in a large open plaza. the entrance to the new stop needs to be both architecturally distinctive and energy efficient, and it must fit within the budget. as part of your summer job with the department of transportation (dot), you've been asked to review three design ideas and recommend which firm should develop its idea into a full design proposal

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?