What is the system of computers, routers, wires, cables, etc. that allow computers to communicate called?

Assume that there is a 4% 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 three independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?

How many nibbles can be stored in a 16-bit word?

Whats three fourths of 15(this is supposed to be in math but i clicked too fast)