After swimming 80 feet below the surface of the water, a whale swims up 40 feet. Use the number line to help you create an equation that shows the new location of the whale in relation to the water's surface. Interpret the sum in the context of the problem.

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?