A solid conducting sphere of radius a has a net positive charge 2Q. A concluding spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge-Q. The surface charge density on the inner and outer surfaces charge density on the inner and outer surfaces of the spherical shell will be

• A. \[-\frac{2Q}{4\pi {{b}^{2}}},\frac{Q}{4\pi {{c}^{2}}}\]
• B. \[-\frac{Q}{4\pi {{b}^{2}}},\frac{Q}{4\pi {{c}^{2}}}\]
• C. \[0,\frac{Q}{4\pi {{c}^{2}}}\] 
• D.        None of the above