4 A car of mass 900 kg is moving on a straight horizontal road \(A B C D\). There is a constant resistance of magnitude 800 N in the sections \(A B\) and \(B C\), and a constant resistance of magnitude \(R \mathrm {~N}\) in the section \(C D\). The power of the car's engine is a constant 36 kW .

1. The car moves from \(A\) to \(B\) at a constant speed in 120 s . Find the speed of the car and the distance \(A B\).
   The car's engine is switched off at \(B\).
2. The distance \(B C\) is 450 m . Find the speed of the car at \(C\).
3. The car comes to rest at \(D\). The distance \(A D\) is 6637.5 m . Find the deceleration of the car and the value of \(R\).