The train traveled 100km (50x2) down and then 375km (75x5) up. So the train is 275km (375-100) up from where it started.
Of course the major needs of a plant is CHLOROPHYLL, because chlorophyll makes the plant green then SUNLIGHT, because the process cant work without energy. Then WATER and CARBON DIOXIDE.
Hoping this could help
I disagree because although recycling is good, Earth firstly is not a closed system and new matter enters the environment all the time, such as comets.
