14. 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] 15. Determine the following: a) Determine the vector equation of the plane that contains the following two lines L1:r = (3, -2,5) + +(2, 1, 4), tER [3] 12:1 = (3, -2,5) + s(4,0,-1), SER b) Determine the corresponding Cartesian equation. [5]