Suppose you deposit $20,000 into a saving account at your local bank. If the bank pays an average interest rate of 5% annually, how much money will you have in your saving account in 15 years?

Suppose, your bank talks you into opening a saving account with them. The bank promises that if you put $10,000 in the saving account today, you will receive $20,000 10 years from now. What is the average interest rate that the bank will pay you over this 10-year period?