A circle of radius 20 cm with centre P lies completely inside another circle of radius 50 cm with centre Q, such that they touch at excatly one point. The centres of these circles are joined to form a line segment PQ. From P and Q, perpendiculars are drawn on the same side such that perpendicular from P intersects small circle at S and perpendicular from Q intersects large circle at R. What will be the area of quadrilateral PQRS?