I am stuck on this problem!

(a) Find the cartesian equation of the plane P through the points

$\displaystyle P(1, 2, 1)$, $\displaystyle Q(2, 1, -1)$, $\displaystyle R(0, 3, 1)$.

(b) Find the equation of the line which is perpendicular to P and passes through the point $\displaystyle S(2, -2, 3)$.

(c) Find the coordinates of the point T on P which is closest to S and hence find the distance from S to P.

Any help is much appreciated,

Dranalion