[SOLVED] Find coefficient of friction?

A picture is attached to a vertical wall by means of string AC with length l forming an angle α with the wall. The height of the picture BC = d. The bottom of the picture is not fastened. At what coefficient of friction between the picture and the wall will the picture be in equilibrium?

For diagram, Mechanics on Flickr - Photo Sharing!

I keep getting the value of μ in terms of weight of the body but that is not a known variable. How to find μ in terms of the lengths given?