NO.PZ2023091701000121
问题如下：
A bank uses a 4-grade scale for its internal credit
model. The 1-year rating transition probabilities for this model are given by:
If a newly issued bond is rated “A” by this model, what is the probability that it will be rated “B” or lower two years from now?
选项：
A.9% B.10% C.18% D.19%解释：
是怎样计算的？
