pls explain each step

Example You want to save enough money for an early retirement at age 60 . You want to live off of $10,000 per month until you die (let's say 30 years). During retirement, your rate of return on your investments will be 0.25% per month. Before retirement, you can earn 0.8% per month on your investments. Assuming you have 35 years until you retire, how much do you need to save per month