Three blocks are in contact with each other

on a frictionless horizontal surface. A 696 N
horizontal force is applied to the block with
mass of 4.7 kg as shown in the figure below.
The acceleration of gravity is 9.8 m/s
2
.
4.7 kg 5.5 kg 7.1 kg

d) What is the magnitude of the force between
the block with mass 5.5 kg and 7.1 kg?