Melissa Gould wants to invest today to assure adequate funds for her son's college education. She estimates that her son will need 20,000 in eighteen years, 25,000 in nineteen years, 30,000 in twenty years, and 40,000 in twenty-one years. How much does Melissa have to invest in a fund today if the fund earns the following interest rate.

a) 6% per year with annual compounding

b) 6% pear year quarterly compounding

c) 6% per year with monthy compounding

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