Solution:
To solve this question, we will use the formula below

Step 1:
Calculate the interest for 20 years( n=20)

Step 2:
Calculate the interest for 25 years( n=25)

The difference in interest will be

Hence,
The final answer is
The difference in interest is $611,800.75 less $389,742.13 or $222,058.62 in savings by financing for 20 years versus 25 years.