3d Geometry

Let the plane \(P:\overrightarrow r \,.\,\overrightarrow a = d\) contain the line of intersection of two planes \(\overrightarrow r \,.\,\left( {\widehat i + 3\widehat j - \widehat k} \right) = 6\) and \(\overrightarrow r \,.\,\left( { - 6\widehat i + 5\widehat j - \widehat k} \right) = 7\). If the plane P passes through the point \(\left( {2,3,{1 \over 2}} \right)\), then the value of \({{|13\overrightarrow a {|^2}} \over {{d^2}}}\) is equal to :