JJ invested $$5,000$ ten years ago and expected to have $$10,000$ today. He has neither added nor withdrawn any money since his initial investment. All

interest was reinvested and compounded annually. As it turns out, he only has $$8,400$ in his account today. Which one of the following statements must

be true?

Multiple Choice

He earned simple interest rather than compound interest.

He did not earn any interest on interest.

He earned a lower interest rate than he expected.

The future value interest factor turned out to be higher than he expected.

He ianored the Rule of $72$ which caused his account to decrease in value.