please explain the answer, Thanks

13. Please explain the purpose of the transaction and the type of risk faced by both parties to the spot commodity of the non-fixed income securities. As for the buyers of the fixed income securities, whether they [hold to maturity] can determine the type of risk they are exposed to, please explain how the type of risk faced by the buyers who hold to maturity is different from the buyers who do not hold to maturity.

14. Given that the announcement mortgage interest rates of three banks A, B and C are 5%, 6% and 7% respectively, and the financing ratio is 7.5%, 8% and 9% respectively, assuming that the housing market crisis occurs and the house price generally falls by 15% to 18%, please explain why the housing interest rate is directly proportional to the financing ratio, and then explain which bank will face the heaviest credit risk and the reasons.