If the earth’s crust contained twice as much iron as it does, would atmospheric oxygen buildup have been slowed down or sped up during the past 2.5 billion years?
what would the consequence of this have been for the evolution of aerobic respiration, the ozone layer, green plants, and animals?

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min