During a flood, the water level in a river firt roe fater and fater, then roe more and more lowly until it reached it highet point, then went back down to it pre- flood level. Conider water depth a a function of time. (a) I the time of highet water level a critical point or an inflection point of thi function? (b) I the time when the water firt began to rie more lowly a critical point or an inflection point?