A demand loan of $8000.00 is repaid by payments of $4000.00 after two years, $4000.00 after four years, and a final payment after six years. Interest is 5% compounded monthly for the first two years, 6% compounded quarterly for the next two years, and 6% compounded annually thereafter. What is the size of the final payment?

The final payment is _____.

(Round the final answer to the nearest cent as needed. Round all intermediate values to six decimal places as needed.)

Please explain step by step.