Needing help on Equity Portfolio Mgmt

Hi all. Thanks for helping in advance.

I refer to CFA Institute official textbook reading 29 exhibit 12. How does one calculate the active risk of the portfolio amounting to 2.4% using the CAV formula?

Thanks.

I don’t know if you can get the 2.4% with just the information provided in this case. I think you would need the index covariances.