Assume a planet having a radius R and its density is expressed as = ( frac{R+r}{2r}D ).

• A. ( frac{5 pi D R^3}{2} )
• B. ( frac{4 pi D R^3}{3} )
• C. ( frac{5 pi D R^3}{3} )
• D. ( frac{5 pi D R^3}{12} )