Two concentric conducting spherical shells of radii \[{{a}_{1}}\]and \[{{a}_{2}}\]\[({{a}_{2}}>{{a}_{1}})\] are charged to potentials \[{{\phi }_{1}}\] and \[{{\phi }_{2}}\], respectively. Find the charge on the inner shell.

• A. \[{{q}_{1}}=4\pi {{\varepsilon }_{0}}\left( \frac{{{\phi }_{1}}-{{\phi }_{2}}}{{{a}_{2}}-{{a}_{1}}} \right){{a}_{1}}{{a}_{2}}\]      
• B. \[{{q}_{1}}=4\pi {{\varepsilon }_{0}}\left( \frac{{{\phi }_{1}}+{{\phi }_{2}}}{{{a}_{2}}+{{a}_{1}}} \right){{a}_{1}}{{a}_{2}}\]
• C. \[{{q}_{1}}=4\pi {{\varepsilon }_{0}}\left( \frac{{{\phi }_{1}}-{{\phi }_{2}}}{{{a}_{2}}+{{a}_{1}}} \right){{a}_{1}}{{a}_{2}}\]
• D. \[{{q}_{1}}=4\pi {{\varepsilon }_{0}}\left( \frac{{{\phi }_{1}}+{{\phi }_{2}}}{{{a}_{2}}-{{a}_{1}}} \right){{a}_{1}}{{a}_{2}}\]