3 wheeled frictionless toys are placed in contact with each other on a frictionless level bench. Their masses are 1.5 kg, 2.0 kg, and 2.5 kg. The 1.5 kg is on one side, 2.0 kg is on the middle, and 2.5 kg is on the other side. A child applies a 15 N force (in the positive direction) on the 1.5 kg toy. Determine the contact force between the 1.5 kg and 2.0 kg toys.