The number density of molecules of a gas depends on their distance r from the origin as, $n ( r ) = n _ { 0 } e ^ { - \alpha r ^ { 4 } }$. Then the number of molecules is proportional to:\\
(1) $n _ { 0 } \alpha ^ { - 3 }$\\
(2) $\sqrt { n _ { 0 } } \alpha ^ { \frac { 1 } { 2 } }$\\
(3) $n _ { 0 } \alpha ^ { \frac { - 3 } { 4 } }$\\
(4) $n _ { 0 } \alpha ^ { \frac { 1 } { 4 } }$