Iwill mark 1st person who is correct brainliest worth 22 points

Which one ? is the answer and how to find this answer

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?

What makes a trapezoid an isosceles trapezoid?