求助一道关于回归方程的题目 expected, standard, returns, annual

Benjiko

Consider two stock A and B. Assume their annual returns are jointly normally distributed, the marginal distribution of each stock has mean 2% and standard deviation 10%, and the correlation is 0.9. What is the expected annual return of stock A if the annual return of stock B is 3%?
A. 2%
B. 2.9%
C. 4.7%
D. 1.1%

the answer is B
怎么利用回归方程解答呢？
望高手解答，谢谢！

adehbone

这不是真题嘛。。。。楼上很好很热心 谢谢