z 3 6. The amount of pollution in a lake is described by the function P(t)= [t5 +2] , where tis in years and P is in parts per million (ppm). Find the rate at which the amount of pollution is changing after 15 years. [4] 7. An object moves along a horizontal line in a way that its position is described by the function s(t) = t3 41,'2 +12t 6, 0 s t S 8, where s is in metres and t is in seconds. [6] a) At what time(s) does the object stop moving? b) At what time(s) does the object have an acceleration of zero? c) Use your previous answers to determine during which time intervals the object is speeding up and slowing down. (Consider setting up a table for this analysis.) 0.0 St 9+4Y' C is in mg/mL and t is in hours. Find the maximum and minimum concentrations for 1 S t S 5 [ 8. The concentration of a drug in a patient's bloodstream is given by C(t)= where