Answer: It is $4429 (interest combined) or $1107.25 (interest annually)
Explanation:
1. Subtract 13400 from 17829:
17829 - 13400 = 4429
2. Now, we know that 4429 is the accumulated interest in 4 years, now divide 4429 by 4:
4429/4 = 1107.25
3. Now we know that 1107.25 is the interest accumulated every year.