Please help and explain

A 2005 study by the Fisheries Research Services in Aberdeen, Scotland, suggests that the average length of the species Clupea harengus (Atlantic herring) as a function of age t (in years) can be modeled by L(t) = 32 (1 - e-0.37t ) cm for 0 s t s 13. L (cm) 32 1 30 20- 10- 2 8 10 12 1 (year) How fast is the length changing at age t = 12 years? (Use e = 2.72. Give your answer to two decimal places.) rate of change of length = cm/yr At what age A is the length changing at a rate of 8 cm/yr? (Use e = 2.72. Give your answer to two decimal places.)