Calculate the convexity for a three-year 4.5% coupon rate with a face value of $500,000 loan with amortised payments? Use this information to determine the impact on the market value of the amortised loan if the entire yield curve shifted downward 50-basis points. What is the usefulness of convexity when duration is available as a measure of interest rate risk? What is the practical implication for the three-year loan in this example?