Strawberry Rhubarb Cobbler

4 C. Rhubarb – chopped
2 10oz. pkgs. Strawberries (thaw if frozen)
2 ¼ C. Sugar
8 T. Minute Tapioca
1 Yellow cake mix
1 Cube Margarine

Put strawberries in blender. Combine strawberries, rhubarb, sugar, and tapioca. Pour into 9x13 pan. Mix cake mix and melted margarine. Sprinkle over fruit mixture. Bake at 350° for 35 to 40 min.