Question : Determine average resistance!

A pile driver hammer of mass 150kg falls freely through a distance of 5 metres to strike a pile of mass 400kg and drives it 75 mm into the ground. the hammer does not rebound when driving the pile. determine the average resistance of the ground.

m1:150kg
m2:400kg
D1: 5m
D2: 75mm
PE:KE
PE:mgh
PE: 150 *9.81* 5
PE: 7357.5 J
KE: 7357.5 J

Speed^2 = 7357.5/ (0.5 * 150)
Speed^2=98.1
speed=9.904 m/s

i have all this information but i do not know how to progress onto the next part of the question. anyone know how to lead me to the next part?

Answer : Determine average resistance!

>> the total momentum of the hammer is transfered to the pile of mass, provided that the hammer does NOT BOUNCE.

Terminology or ?

Assuming no bounce, I wouldn't say that this is transferring the entire momentum to the pile of mass, since both the hammer and the pile of mass are now both moving with the same speed.