According to the Rule of 72, how long would it take for $2500 to become $80,000?

According to the Rule of 72, how long would it take for $2500 to become $80,000? A. approx. 40 years at 7.2% interest B. approx. 54 years at 12% interest C. approx. 96 years at 6% interest D. approx. 30 years at 14.4% interest E. approx. 50 years at 7.2% interest