Blocks with masses of 30 kg 40 kg and 50 kg are lined up in

Question

Compute all parts of given problem:

Problem: Blocks with masses of 3.0 kg, 4.0 kg, and 5.0 kg are lined up in a row on a frictionless table. All three are pushed forward by a 20N force applied to the 3.0 kg block.

Part A: How much force does the 4.0 kg block exert on the 5.0 kg block?

Part B: How much force does the 4.0 kg block exert on the 3.0 kg block?

I want help to find how much force does the 4.0 kg block exert on the 5.0 kg block.