(a) Determine the vector equation of the line passing through the (x, y)points (A, B) and (C,D), and write down the coordinates of the two points of intersection with the

coordinate axes. \text { (b) This question concerns vectors } \boldsymbol{a}=\boldsymbol{i}-\boldsymbol{j}-A \boldsymbol{k} \text { and } \boldsymbol{b}=B \boldsymbol{i}+\boldsymbol{j}+C \boldsymbol{k} \text {. } (i)Compute the scalar product of the two vectors and hence find the angle between the two vectors. (ii)Determine a unit vector that is perpendicular to both a and b.