The table shows the proof of the relationship between the slopes of two perpendicular lines. what is the missing statement in step 5?

a. slope of qs x (-slope of us) = 1

b. slope of qs x slope of us = 1

c. slope of qs x slope of us = x

d. slope of qs x slope of us = - x

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?