Space between two concentric conducting spheres of radii a and $\mathrm { b } ( \mathrm { b } > \mathrm { a } )$ is filled with a medium of resistivity $\rho$. The resistance between the two spheres will be:\\
(1) $\frac { \rho } { 4 \pi } \left( \frac { 1 } { a } + \frac { 1 } { b } \right)$\\
(2) $\frac { \rho } { 2 \pi } \left( \frac { 1 } { a } + \frac { 1 } { b } \right)$\\
(3) $\frac { \rho } { 4 \pi } \left( \frac { 1 } { a } - \frac { 1 } { b } \right)$\\
(4) $\frac { \rho } { 2 \pi } \left( \frac { 1 } { a } - \frac { 1 } { b } \right)$