The driver of a three wheeler moving with a speed of 36 km see a child standing in the middle of the road and brings his vehicle to rest in 4 s, just in time to save the child

The driver of a three wheeler moving with a speed of 36 km see a child standing in the middle of the road and brings his vehicle to rest in 4 s, just in time to save the child. What is the average retarding force on file vehicle . The mass of the three wheeler is 400 kg and the mass of the driver is 65 kg.