Could anyone please tell me how the standard deviation is calculated in the question? For instance on page 191 we have: Equity market value 5775,4 and beta 0.98. How do you get ?S=?m*? of 7.84% same with debt and then total: total market value 8684,3 , beta 0.6936, how do you get ?S=?m*? of 5.5488%