Alex is adding baseball cards to sleeves in his binder. He filled 2/7 of his binder the first day. On the second day he filled 4/7 . How much of his binder did Alex fill in those two days? A) 3/7 B) 4/7 C) 5/7 D) 6/7

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?