NEED ANSWERS NOW!! (Reward) brainlest and pointsss

How can constraints be used to model a real-world situation?

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?

Which represents the number of times all outcomes less than a given outcome occur? cumulative frequency relative frequency frequency cumulative relative frequency