Suppose a cylindrically shaped drop of water at $25$ oC$,2$ mm in radius, is positioned on an inclined surface of a microscopically rough material. The slope of the inclined surface is progressively increased, and it is found that the drop remains pinned and does not flow until a critical angle $\backslash$alpha of the inclined plane with the horizontal is attained. If the advancing and receding contact angles of the drop are $\backslash$theta $\backslash$Alpha $=120$o and $\backslash$theta R $=45$o respectively, at what critical angle $\backslash$alpha will the drop flow down the inclined surface?