8 --- ube 10 30 20 10 so 100 200 b) (10 pts) Now suppose that, over the last five years, the phosphorus concentration has gradually increased from 50 to 150 g/l, while the vegetation coverage has gradually decreased from 40% to 37.5% (same as in the individual part). A (new) argument used by interest group B is that even if an increase of the phosphorus level from 150 to 250 ug/l lead to a sharp decrease of vegetation, one could then curb the use of phosphorus. This would bring the phosphorus level back to 150 mg/l and the lake vegetation to 37.5%. In view of our model, to what extent does this argument hold? Explain