set up an integral that represents the length of the part of the parametric curve shown in the graph. x = 9t2 − 3t3, y = 3t2 − 6t. The x y-coordinate plane is given. The curve starts at the point (12, 9), goes down and left becoming more steep, changes direction at approximately the origin, goes down and right becoming less steep, changes direction at the point (6, −3), goes up and right becoming more steep, changes direction at the approximate point (12, 0), goes up and left becoming less steep, and stops at the point (0, 9).