please show step-by-step on how to solve both questions

1) The rate at which a substance grows is given by 150 e.2x where x is the time (in days) What is the total accumulated growth during the first 3 days ? 2) A scientific study conclude that a Eucalyptus tree will grow at the rate of . 6 + 4(t + 1)-3 ft per year , where t is time (in years) Then find a) The number of feet that the tree will grow in the second year ? b) The number of feet the tree will grow in the Third year