Achange to one aspect of the food web cause multiple chain reactions within the system?

Yes, because if one animal goes extinct, contracts a disease, etc. it can cause harm to the other animals that consume it. If a species of rabbit in a forest became extinct then all the animals that consumed the rabbit species as apart of a regular diet will either have to find a new food source or go hungry, which can detriment other species and cause them to go extinct if their numbers are not plentiful.

$100. 125 x 0.20 = 25125 - 25 = $100