Van der waals forces can best be described as the attractive or repulsive forces that are formed
here are the options:
a: between oppositely charged ions in a crystal.
b: during dipole-dipole interactions between molecules.
c: when molecules move apart in the absence of other forces.
d: by a random, short-lived redistribution of electrons.

positive reinforcement? ?

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