The figure below is made up of 3 rectangles X, Y and Z placed such that they overlap at S and T. The ratio of the area of Rectangle X to the area of Rectangle Y to the area of Rectangle Z is 6 : 4 : 1. The ratio of the area of Rectangle S to the area of Rectangle T is 3 : 1. If the area of Rectangle Y is twice that of Rectangle S, what is the ratio of the total area of shaded parts to the total area of the unshaded parts?
