Cassandra invested $650 at the end of every month in an investment fund that was earning interest at a rate of 4.98% compounded monthly. He stopped making regular deposits at the end of 9 years when the interest rate changed to 6.84% compounded quarterly. However, he let the money grow in this investment fund for the next 3 years.

Calculate the accumulated balance in his investment fund at the end of 9 years.

Calculate the accumulated balance in his investment fund at the end of 12 years.

Calculate the total interest earned over the 12-year period.