A demand loan of $8000 is repaid by payments of $3000 after 15 months, $4000 after 30

Question:

A demand loan of $8000 is repaid by payments of $3000 after 15 months, $4000 after 30 months, and a final payment after 4 years. If interest was 8% for the first two years and 9% for the remaining time, and is quarterly, what is the size of the final payment?
Compounding
Compounding is the process in which an asset's earnings, from either capital gains or interest, are reinvested to generate additional earnings over time. This growth, calculated using exponential functions, occurs because the investment will...