A dollar store sells items for $1 and $2. You plan to go there and spend at least $20. Let x stand for the number of one-dollar items and let y stand for the number of two-dollar items. Write and graph a linear inequality that models the situation.

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?