4. a. Calculate a x E, where d = (1,2,1) and E' = (2, 4,2). b. If a and 3 represent the sides of a parallelogram, explain why your answer for part a. makes sense, in terms of the formula for the area of a parallelogram. 5. A line passes through the points M(4, 5) and N(9, 5). a. Sketch this line. b. Determine vector and parametric equations for this line. 6. Two lines have equations 2x 3y + 6 = 0 and 4x 6y + k = 0 a. Explain, with the use of normal vectors, why these lines are parallel. b. For what value of k will these lines he co incident