Ateam of eight dogs pulls a sled with waxed wood runners on wet snow ( the dogs have average masses of 19.0 kg, and the loaded sled with its rider has a mass of 210 kg. (a) calculate the magnitude of the acceleration starting from rest if each dog exerts an average force of 185 n backward on the snow. (b) what is the magnitude of the acceleration once the sled starts to move? (c) for both situations, calculate the magnitude of the force in the coupling between the dogs and the sled.