Pearl deposited $60 into a savings account for which interest is compounded monthly. According to the rule of 72, what interest rate will cause her money to double in approximately 33 years? A. 2.2% B. 0.6% C. 0.5% D. 1.8%

The rule of 72 says that the time it takes to double an investment is approximately equal to 72 divided by the interest rate in %.

Thus
33 years =72/i  => i=72/33=2.18%, or approximately 2.2%.