Mariana had a $20 gift card to an online music store. she spent the entire amount on songs, which cost $1 each, and music videos, which cost $2 each. mariana bought 5 more songs than music videos. write and solve a system of equations to find the number of songs and the number of videos mariana bought.

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?