(a) Relative to an origin O, the position vectors of the points A, B and C are given by OA=i- j+2k, OB =-i+j+k and OC = j+ 2k respectively. Let ll is the plane containing OA and OB (1) (ii) Show that OA and OB are orthogonal. Determine if OA and OB are independent. Justify your answer. Find a non-zero unit vector n which is perpendicular to the plane II