At age ​20, to save for​ retirement, Rebecca decides to deposit 80​$ at the end of each month in an IRA that pays 6.2% compounded monthly. Use the formula for the value of an annuity. A=P[(1+r/n)^nt-1]/(r/n)

How much money will be in the IRA when Rebecca​ retires?

How much interest will the IRA have​ gained?

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?