Is there any combination of facebook Unity Android SDK with google AdMob plugins or how to do that?

Now I'm using v.5.1 facebook Unity SDK for Android and my game is almost done very well.

I just realized that I should make some profit with adMob, so I tried to import admob plugin(Mics) then modify the AndroidManifest by adding new activity that does not exist in the old one.

but this make my game crash when try to FB.Inint() but admob works well.

I'm quite new for android development and don't know exactly how the plugins works.

Can anyone explain or suggest what should I do to get these plugins works in a game?

Thanks a lot :)