$3.$ A couple has a $30$ year, $4\%$ annual interest rate mortgage on a property that was worth $$300,000$ at the time they bought it$.$

They originally put $20\%$ down. What would be their monthly payment?

After $5$ years, they are thinking of paying off the mortgage by adding $$100$ a month to their payment.

Their other choice is to take the $$100$ a month and put it in a high yield savings account earning $4\mathrm{.}3\%$ a year.

How long will it take to pay off the mortgage by adding the extra $$100$ a month to the payment?

What would be the total savings from paying off the mortgage? Using the length of time it takes to pay off

the mortgage after the initial $5$ years, how much would the $$100$ a month be worth if put in the high yield savings account? Which is better? Why?

Using the length of time it takes to pay off the mortgage after the initial $5$ years,

how much would the $$100$ a month be worth if put in the high yield savings account? Which is better? Why?