please use excel to solve both question a) and the bonus. also please explain the bonus question which rate we use first and why and then explain which rate we use next. thank you

Suppose you wish to retire 33 years from today. You determined that you would need $250,000 per year after you retire, with the first retirement funds withdrawn one year from the day you retire and that you will need to make 25 such withdrawals. If you can earn 5% per year on your retirement funds. a) How much must you deposit in an account today (lump sum), so that you may have enough funds for retirement? Bonus: Rework (a) assuming you can earn 5% interest until you retire then will earn only 4% thereafter