How much money will Sarah need to save per month to reach her goal of $20,000 given the following:

-Sarah is 35 years old

-Sarah needs the $20,000 by the age of 65 years old.

-Her before-tax-return is 8%

-Her Marginal tax bracket percent is 25%

AND how much money will Sarah need to save per month to reach this goal if she waits 5 years before she starts saving?

I am also given this chart that shows the answers, but I need to know how they did this:

I am also told this: By waiting 5 year(s) to begin saving annually for her $20,000 goal, it will cost her an additional $1,661.

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