Answer:
6.78% per year.
Step-by-step explanation:
Assuming compounding occurs only once a year, the interest rate 'r' required on a $2,000 investment for 4 years to yield $2,600 is determined by:
![FV = PV*(1+r)^n\\2,600 = 2,000*(1+r)^4\\r=\sqrt[4]{(2,600)/(2,000)}-1\\ r=0.06779=6.78\%](https://img.qammunity.org/2021/formulas/business/college/pfmvzbgg8plb6mmfvxjlfy790re0yqsh4l.png)
The interest rate earned on those savings was 6.78% per year.