15. Points: A(-4, 3, 4), B(-5, 2, 5), and C(-3, 1, 5) form a triangle. Find a vector that has a magnitude of one and is perpendicular to the triangle. [3 marks] 16. Determine, showing work, whether the plane m: 3x - y - z - 6 = 0 contains the line [x, y,z] = [3, -1, 4] + s[2, 3, 3] [2 marks] 17. The point (a, b, -) lies on the line L1: [x, y, z] = [3, -1, 4] + s [4, 3, -1] Determine the values of a and b. [2 marks]