Please help me on part a and after part a I will send you part b

If u good at math hit me up on insta or sum @basic_jaiden or @ and

An object in geometry with no width, length or height is a(n):

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?