456 students participated in switch day the students raised money for charity so that the principal would approve of the day if the total amount of money raised was $912 and each student brought in the same amount of money how much did each student raise?

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?