Danielle invested $1,800 at the beginning of every 6 months in an RRSP for 11 years. For the first 9 years it earned interest at a rate of 3.10% compounded semi-annually and for the next 2 years it earned interest at a rate of 6.80% compounded semi-annually.

a. Calculate the accumulated value of his investment at the end of the first 9 years.

b. Calculate the accumulated value of her investment at the end of 11 years.

c. Calculate the amount of interest earned from the investment.