A graduated cylinder is partially filled with water with a measured volume of 11.33 mL. A sphere of lead (density = 11.34 g/mL) and a sphere of platinum (density = 21.40 g/mL) are placed inside the graduated cylinder. The water level rises to 21.57 mL as a result of the addition of the two metal spheres. If the masses of both spheres total 241.485 grams, what is the radius of the platinum sphere in units of cm?