Q$2.(5$ points$)$ Let $P$ be the plane given by $x+2y+6z=6.$

a$)(2$ points$)$ Denote by A the point with coordinates $(1,1,1),$ find the distance between A and $P.$

b$)(3$ points$)$ Let $v$ be a vector. The vector projection of $v$ onto the plane $P,Pro{j}_{P}v,$ can be defined informally as follows: Suppose the sun is shining so that its rays are normal to the plane $P.$ Then $Pro{j}_{P}v$ is the "shadow" of $v,$ with the tail onto $P.$ Find $Pro{j}_P$vec$(OA).$