Qawa river in Labasa is polluted and its amount is found to be A(t) = 5(5+1 /3 + 10 )", where A is the amount and t is the time in years. a). Find the instantaneous rate of change of the amount of pollution in Qawa river. b). At what rate is the amount of pollution changing after 20 years? [3 + 1 = 4 marks]