Caleb invested $875 at the end of every month in an investment fund that was earning interest at a rate of 4.38% compounded monthly. He stopped making regular deposits at the end of 6 years when the interest rate changed to 6.99% compounded quarterly. However, he let the money grow in this investment fund for the next 2 years.

Calculate the accumulated balance in his investment fund at the end of 6 years.

b. Calculate the accumulated balance in his investment fund at the end of 8 years.

c. Calculate the total interest earned over the 8-year period.