What was the potential energy of truck 1 at the top of the hill?

You are a traffic accident investigator. You have arrived at the scene of an accident. Two trucks of equal mass(3,000 kg each) were involved in a rear-end accident at a stop sign. here is what you know:
Truck 1 approched the intersection from the top of a 22-meter hill.
Truck 2 was on a flat stretch of road directly in front of truck 1.
At the bottom of the hill, before braking for the stop sign, Truck 1 was going 20 m/s and truck 2 was going 35 m/s.
From the skid marks on the road you can see that truck 1 applied force on its brakes for 2 seconds, 80 meters before the stop sign.
There were no skid marks left by truck 2. The collision occured at the stop sign, where truck 2 had stopped.
After the collision, both trucks were moving together in the same direction at 10 m/s, before slowly rolling to a stop.
You must now push truck 2 using 1,000 N of force, 8 meters off the side of the road so no one else gets hurt.