Blocks K and L move towards one another on a horizontal frictionless surface. The diagram indicates the momentum of the two blocks immediately before they collide. While the collision takes place, the blocks remain in contact for $0.084\,\text{ s}$. Once the collision is over, the blocks move apart and block L travels back along its initial path with momentum $0.12\,\text{kg m s}^{-1}$. Determine the magnitude of the average force on block L due to block K during the collision.
- A$3.1\,\text{N}$
- B$4.0\,\text{N}$
- C$6.9\,\text{N}$
- D$7.1\,\text{N}$