8. The vertices of a quadrilateral ABCD are A [0,3,5], B [-3, -1,17], C[4, -3,15] and D [7,1,3] Prove that ABCD is a parallelogram. [5] 9. Determine the following: c. Determine the vector equation of the plane that contains the following two lines L1: r =(4, -3,5) + t(2,0,3), teR and L2: r=(4, -3,5) + s(5,1, -1),SER [3] d. Determine the corresponding Cartesian equation. [5]