In each case, find a vector equation of the line.
(a) Passing through P(2, -1, 3) and perpendicular to the plane 2x + y = 1.
(b) Passing through P(1, 1, -1), and perpendicular to the lines [x y z]T = [2 0 1]T + t[1 1 -2]T and [x y z]T = [5 5 -2]T + t[ 1 2 -3]T.
(c) Passing through P(1, 1, 2), intersecting the line [x y z]T = [2 1 0]T + t[1 1 l]T, and perpendicular to that line.