Answer: $1,603.93
Step-by-step explanation:
APR is monthly so figures have to be adjusted to monthly figures for a year.
If you fail to improve your credit score, the interest you will pay is:
= 25,000 * [(1 + 30%/12)¹² - 1]
= $8,622.22
If you improve your credit score, your APR will decrease to 25.0% from 30%.
Interest paid would be:
= 25,000 * [(1 + 25%/12)¹² - 1]
= $7,018.29
Savings = 8,622.22 - 7,018.29
= $1,603.93