A filmmaker wants to achieve an interesting visual effect by filming a scene through a converging lens with a focal length of 50.0 m. The lens is placed between the camera and a horse, which canters toward the camera at a constant speed of 7.0 m/s. The camera starts rolling when the horse is 40.0 m from the lens. Find the average speed of the image of the horse
(a) During the first 2.0 s after the camera starts rolling
(b) During the following 2.0 s.