please use equations. No excel. Thank you!

14. Your grandfather left you $40,000 when he died. You can invest the money to earn 9% per year. - If you spend $7227 per year out of this inheritance, how long will the money last? - If you spend $3600 per year, how long will the money last? - What is the most you can spend in equal annual amounts from your inheritance for the next 20 years