Answer:
if you want to achieve your goal in 20 year, you would have to invest 1879.790424 at the end of each month for 240 months. you will have 800,000 after 20 years.
Explanation:
rate of return is 5.3% compounded monthly.
number of years = 40.
future value = 800,000
interest rate per month is 5.3% / 12 = .4416666....%
number of time periods if 40 * 12 = 480
payment required at the end of each month is equal to 484.5267545
your total payments are 480 * 484.5267545 = 232,572.8422
total interest earned would be 800,000 minus 232,572.8422 = 567,427.1578
if you want to achieve your goal in 20 year, you would have to invest 1879.790424 at the end of each month for 240 months.
you will have 800,000 after 20 years.
if you deposit that money for an additional 10 years at the same rate of interest per year compounded annually, then you will have 1,357,560.674.
you can use an online calculator to get the results similar to this.
they might not be right on because of possible rounding errors, but they'll be close.