Patch for the lastest zero day vulnerability

Hi

Microsoft has released a patch for the latest zero day vulnerability. In the pagehttps://support.microsoft.com/kb/2887505 it is written:

"You must have security update 2870699 installed for this Fix it to provide effective protection against this issue."

Question: What happens if this path is installed and 2870699 has not been installed yet?

a: Will not provide effective protection against this issue before 2870699 has been installed - but work fine when it has been installed?

or

b: Will never provide effective protection against this issue if 2870699 is installed after the fix in 2887505.

Thanks in advance

Best regards Harald