How are point source and nonpoint source pollution harmful when it rains

Nonpoint source pollution is difficult to control because it comes from many different sources and locations. Most nonpoint source pollution occurs as a result of runoff. When rain or melted snow moves over and through the ground, the water absorbs and assimilates any pollutants it comes into contact with.

it should be p1 v1 = p2 v2

i think its 100.

hope this !