The equations of the sides $AB , BC \& CA$ of a triangle $ABC$ are $2x + y = 0 , x + py = 21a ( a \neq 0 )$ and $x - y = 3$ respectively. Let $P ( 2 , a )$ be the centroid of the triangle $ABC$, then $( BC ) ^ { 2 }$ is equal to
The equations of the sides $AB , BC \& CA$ of a triangle $ABC$ are $2x + y = 0 , x + py = 21a ( a \neq 0 )$ and $x - y = 3$ respectively. Let $P ( 2 , a )$ be the centroid of the triangle $ABC$, then $( BC ) ^ { 2 }$ is equal to