Points A and B have position vectors (2, 1, 4) and (2λ, λ, 4λ).(a) Show that B lies on the line OA

Points A and B have position vectors (2, 1, 4) and (2λ, λ, 4λ).
(a) Show that B lies on the line OA for all values of λ.
Point C has position vector (12, 2, 4).
(b) Find the value of λ for which CBA is a right angle.
(c) For the value of λ found above, calculate the exact distance from C to the line OA.