Does anyone know what shape this is?

The forerunner to cell phones, pdas, and smartphones was

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?

One of your customers wants you to build a personal server that he can use in his home. one of his concerns is making sure he has at least one backup of their data stored on the server in the event that a disk fails. you have decided to back up his data using raid. since this server is for personal use only, the customer wants to keep costs down. therefore, he would like to keep the number of drives to a minimum. which of the following raid systems would best meet the customer's specifications? a. raid 0 b. raid 1 c. raid 5 d. raid 10