Please help me with these questions

(a) The population of bacteria grows at a rate that slows down with time and the growth rate after t days is given by P'(1) - 4000 for t > 2. Given that the ( 2t - 3) 2 population is 20000 when t = 2, find the population when t = 6. ( 5 marks ) (b ) An environmental protection group estimates that the rate of dumping of toxic chemicals from a manufacturing plant in gallons per year is given by R (t ) 1000 ( 1 +t )2 where t is the time in years since the plant started operation (t = 0) before any dumping began. (i) Determine the rate of dumping toxic chemicals by the plant at the end of the fourth year. ( 2 marks ) (ii) Find an expression Q(t) for the amount of toxic chemicals dumped by the power plant in t years. ( 6 marks ) (iii) Find the total amount of toxic chemicals dumped at the end of ninth year on the operation of the plant. ( 2 marks )