You decide to open an individual retirement account (IRA) at your local bank that pays 8 percent/year compounded annually. At the end of each of the next 40 years, you will deposit $4,000 into the account. Three years after your last deposit, you will begin making annual withdrawals. What annual amount will you be able to withdraw if you want the withdrawals to last

a. 20 years?

b. 30 years?

c. forever?