John is 25 years old now and he is expecting to retire in 40 years. He would like to have $5,000,000 at the date of retirement. How much should he save per month to reach this goal if interest rate is 6% per annum? 

If John expects that he will live for 20 years after retirement, how much can he withdraw from his retirement account, which is $5,000,000 at the date he retires, per month, if the interest rate is also 6%?

If John would like to be able to spend $30,000 per month rather than the earlier amount calculated in his retirement period, how much should he have at the date he retires?