Let the lengths of intercepts on $x$-axis and $y$-axis made by the circle $x ^ { 2 } + y ^ { 2 } + ax + 2ay + c = 0 , ( a < 0 )$ be $2 \sqrt { 2 }$ and $2 \sqrt { 5 }$, respectively. Then the shortest distance from origin to a tangent to this circle which is perpendicular to the line $x + 2y = 0$, is equal to :\\
(1) $\sqrt { 11 }$\\
(2) $\sqrt { 7 }$\\
(3) $\sqrt { 6 }$\\
(4) $\sqrt { 10 }$