The point P is the intersection of the straight line joining the points Q(2, 3, 5) and R(1, –1, 4) with the plane 5x – 4y – z = 1. If S is the foot of the perpendicular drawn from the point T(2, 1, 4) to QR, the length of the line segment PS is
(a) 1/√2
(b) √2
(c) 2
(d) 2√2