It's hard to tell what is going on without a schematic. Best thing is to post an image at an image-hosting site, like www.photobucket.com
or www.imageshack.com
and then post a link to it here.
Also, you'll need to post how far you got or how much you know about solving the problem (Physics Forum policy).
p.s.
Thanks for posting here, if we did homework help in the Chat Room then the helpers would stop showing up there.