How do you beat level 16 of the game vehicles?

How do you beat level 16 of the game vehicles?
1st you have to let the ambulance drop. click on the ambulance so that it pushes the bar out of the way and drops down to push the big van of the cliff but be carefull not to fall with it.
then let the fire truck drop. click on the firetruck so that it pushes the bar back to its place, then throuwing the little car on the other side off the cliff.

finally let the police car drop. click on it so you can park it in the green zone.