Greg is bowling with his friends and rolls the ball at time t = 0. Consider the center axis of the lane to correspond to line x = 0 and the pin deck to be at the line y = 15. The gutters correspond to the lines x = -4 and x = 4. If a ball falls into a gutter before hitting any pins, Greg’s score is 0. The motion of the ball can be described by the parametric functions y(t) = -4t^2 + 16t and x(t) = -2t. Find the parametric second derivative d^2y/dx^2 of the ball’s motion.