If I have $500 in the 1st month and I divide it in 5 parts and invest it in 5 different on total the next month I get double the profit Everymonth this happens I take ¼ of the money for my needs and invest the ¾ If I started at the age of 10 and stopped at 40 how much money will I have that time​

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?