A portfolio has a mean value of $60 million and a daily standard deviation of $8 million. Assuming that the portfolio values are normally distributed, the lowest value that the portfolio will fall to over the next three days and within 99% probability is:
A
$4.5 million
B
$24.3 million
C
$30.6 million
D
$42.1 million
解析中SD=8*根号3,请问老师公式不是标准差/根号N吗?没有看懂答案谢谢老师