For c>0, if ai +bj + ck is the unit normal vector at (1, 1, 2) to the cone z yx* +y', then a +b-c =0 (b) a-b +c =0 d)a+b +c* =0 (a) (c) -a +b +c* =0

For c>0, if ai +bj + ck is the unit normal vector at (1, 1, 2) to the cone z yx* +y', then a +b-c =0 (B) a-b +c =0 D)a+b +c* =0 (A) (C) -a +b +c* =0