LOTS OF POINTS

How much time would it take a crane to unload a railroad car of scrap metal if:

1. The total load of scrap metal weighs 50,000 N
2. The crane must carry the load a distance of 20 meters.
3. The power of the crane is 2,000 Watts.
4. The crane can carry 3,000 N of metal at a time.
5. It takes 30 seconds for the crane to pick up the load, carry it 20 meters, drop it and return to the railroad car.

Please solve and give an explanation.