(4) (7 points) (a) (3 points) Use vectors to determine whether the triangle with vertices P(1, -3, -2) Q(2,0, -4) and R(6, -2, -5) is a right angled triangle. (b) (2 points) Compute the area of the triangle whose vertices are points P, Q, and R above. (c) (2 points) If a = (3,0, -1), find a vector b such that the scalar projection of b onto a is 2