Assume that there is a 10% 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 diskdrive, what is the probability that during ayear, you can avoid catastrophe with at least one workingdrive?

b. If copies of all your computer data are stored on four independent hard diskdrives, what is the probability that during ayear, you can avoid catastrophe with at least one workingdrive?

a. With two hard diskdrives, the probability that catastrophe can be avoided is

nothing

.

(Round to four decimal places asneeded.)