5. Determine if the vectors a = (5, 4, -1), b = (9, 15, -1), c = (4, -2, 1) are coplanar. [4] 6. Find the magnitude and direction of the resultant and equilibrant of forces of 9 N and 15 N acting at an angle of 270 to each other. Illustrate your solution with a neatly labeled diagram. [3 ] 7. Let A(3,1, -1) , B(1, -1,1), and C(2,0,4) vertices of a triangle a) Find angles of this triangle. [3 ] b) Find out area of triangle. [4]