Created Unassigned: Regarding installing 'Newtonsoft.Json 5.0.4' package [3295]

While installing NewtonSot..Json package, I m getting following Error.

Successfully installed 'Newtonsoft.Json 5.0.4'.
Successfully uninstalled 'Newtonsoft.Json 5.0.4'.
Install failed. Rolling back...
Could not install package 'Newtonsoft.Json 5.0.4'. You are trying to install this package into a project that targets 'Silverlight,Version=v4.0,Profile=WindowsPhone71', but the package does not contain any assembly references that are compatible with that framework. For more information, contact the package author.