Principals of finance; using either excel time value functions or formula time value functions, the fathers age has to me calculated. I am not sure how to factor in all of the different ages. A formula answer would be great, thanks!

4 Your father tells you that he started with the following amount of savings at age 21, and retired with the following amount after earning the given rate on his savings over those years. Your father would never tell you his age - can you figure it out? Age when savings were deposited Starting Balance Ending Balance: Rate earned: Years since retirement: 21 50,000 750,000 5.6% 5 Your father's age