When my sister was born, my parents put 1300 dollars into an account earning 4 percent effective interest. When I was born, my parents put 4000 dollars into the same account. Today is my birthday, and my sister is twice as old as I am. Today the account balance is 12052.4 dollars. When I turn 21, my sister and I will be allowed to use the money in the account. What will the account balance be then? (Hint: First figure out how old I am.)
Answer = dollars.