A 5-column table has 4 rows. The first column has entries A, B, C, Total. The second column is labeled X with entries 10, 110, 60, 180. The third column is labeled Y with entries 80, 44, 59, 183. The fourth column is labeled Z with entries 61, 126, 110, 297. The fifth column is labeled Total with entries 151, 280, 229, 660. Which statement is true about whether Z and B are independent events?

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?