Taking Moments Propped Cantilever

Hello all

I was hoping someone could shed some light on the following question:-

I have a propped cantilever beam as shown below:-

[ATTACH=CONFIG]2597[/ATTACH]


I want to work out the vertical reactions at support A and B.

I have been told to work out the vertical reactions I need to take moments about support B and by doing so the reactions at support B "disappear" - my question is if I take moments about support B do ALL of the reactions disappear and if not which ones remain and which ones disappear?

I hope this makes sense.

Thank you.

See:

[url]https://www.engineersedge.com/beam_bending/beam_bending17.htm[/url]