Determin if this is a function

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 is the volume of a rectangular crate that has dimensions 9 inches by 9 inches by 1 feet? 1,458 in.3 121.5 in.3 1,012.5 in.3 36 in.3

Consider the sequence below. 3 , 1 , 1/3 , 1/9 , select the explicit function which defines the sequence.