Find each of the following:
a. The line through the point (1, 3, 6) perpendicular to the plane x - 2y + 2z = 8.
b. The plane through the points (1, -2, 0) and (0, -2, 4) and containing the line: x = 1 + 2t, y = - (2 + t), z = 4t.
c. The cosine of the angle between the planes 4x + 12y + 3z = 30 and 3x - 2y + 3z = 8.