The pumpkin patch had two corn mazes, as shown by the shaded and non-shaded sections in the model below. A model with 4 rows of 7 squares, representing 28 acres, and 2 rows of 7 squares, representing 14 acres.

Which expression is shown by the model?

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?