A Locomotive Is Pulling Three Train Cars Along a Level

Short Answer

A locomotive is pulling three train cars along a level track with a force of 100,000 N. The car next to the locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. You can neglect the friction on the cars being pulled.
(a) What is the magnitude of the force between that the 80,000-kg car exerts on the 50,000-kg car?
(b) What is the magnitude of the force that the 50,000-kg car exerts on the 70,000-kg car?