(2) 當市場報酬為 5% 或 20% 的機率相等，且國庫券利率水準為 8% 時，兩支股票的預期報酬率分別為何？(5分)

8. A bond's rating provides a guide to its price. As we write this in 2009, Aaa bonds yield $5.45\%$ and Baa bonds yield $8.67\%$. If some bad news causes a $10\%$ five year bond to be unexpectedly downrated from Aaa to Baa, what would be the effect on the bond price? (Assure annual coupons with face value $1,000) (10分)