Robbie plans to retire in 20 years and has just established a personal retirement account where the annual return rate is 6%. If at the end of every month in the coming 20 years, Robbie will deposit $400 in the retirement account, whats the monthly amount (at the end of each month) he can withdraw from this retirement account in the 10 years after retirement (Robbie will have a zero balance after the last withdrawal)?

Please show work with formulas and timeline if possible