If i have 20 apples and my friend has 71 oranges and we add 13 bags of grapes and in each bag holds 60 grapes how much food do we have. this is a 20 point's and answer in the comment box be for u summit it so u don't get it wrong

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?