= The questions and problems that follow refer to Appendixes 12A and 12B. Refer to the information in Appendix 12A for problems 20 and 21. From Table 12A–1 , what is the probability of a loan upgrade? A loan downgrade? What is the impact of a rating upgrade or downgrade? How is the discount rate determined after a credit event has occurred? Why does the probability distribution of possible loan values have a negative skew? How do the capital requirements of the CreditMetrics approach differ from those of the BIS and the Federal Reserve System?