Please help!
Don't mind the one with the answer. Please just answer them all.

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?

Use the given information to determine the exact trigonometric value.

Complete the frequency table: method of travel to school walk/bike bus car row totals under age 15 60 165 age 15 and above 65 195 column totals 152 110 98 360 what percentage of students under age 15 travel to school by car? round to the nearest whole percent.