CAT 2009 : Quant problem on Mensuration

A tower has the following shape: a truncated right circular cone one with radii 2R (the lower base) and R ( the upper base) and height R bears a right circular cylinder whose radius is R, the height being 2R. Finally a semisphere of radius R is mounted on the cylinder. Suppose that the cross-sectional area S of the tower is given by f(x) where x is the distance of the cross-section from the lower base of the cone.
The range of f(x) is

1. [0,4πR²]
2. [πR²,4πR²]
3. [0,πR²]
4. [πR²,3πR²]

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