Future Value of an Annuity for Various Compounding Periods

Find the future values of the following ordinary annuities:

FV of $600 paid each 6 months for 9 years at a nominal rate of 12%, compounded semiannually. Round your answer to the nearest cent. $

FV of $300 paid each 3 months for 9 years at a nominal rate of 12%, compounded quarterly. Round your answer to the nearest cent. $

The annuities described in parts a and b have the same amount of money paid into them during the 9-year period and both earn interest at the same nominal rate, yet the annuity in part b earns more than the one in part a over the 9 years. Why does this occur?