8. You are planning to save for retirement over the next 25 years. To do this, you will invest $3,000 a quarter in a stock account and $1,000 a quarter in a bond account. These investments will be made at the beginning of each quarter. The return of the stock account is expected to be 8%, and the bond account will pay 4%. When you retire, you will combine your money into an account with a 6% return. How much can you withdraw each month (starting one month from the retirement date) from your account assuming a 20-year withdrawal period?

Could you explain the question in detail with formula plz! I don't understand others poster answers.