Sentence:  A zone of a sphere is the curved surface of a frustum....Determine, correct to 3 significant figures (a) the volume of the frustum of the sphere, (b) the radius of the sphere and (c) the area of the <WSD>zone</WSD> formed. 
Meaning of the word marked with <WSD> tags:  The curved surface of a frustum of a sphere, the portion of surface of a sphere delimited by parallel planes.