30. If the correlation coefficient between Baker Fund and the S& 500 Stock Index is 0.70, what
percentage of Baker Fund's total risk is specific (i.e., unsystematic)?
 
A.  35%.
B.  49%.
C.  51%.
D.  70%. 
 
 这道题是98sample上的 不太明白 哪位牛人给解释下吧 多谢多谢

R^2 = rho^2,

R^2 ==> systematic risk

1-R^2 or 1-rho^2 ==> unsystematic

for this specific question, rho=.7, therefore, R^2=.7*.7=.49, the systematic risk is .49, then you can get unsystematic risk is .51 under the assumption "total risk = systematic risk + unsystematic risk"