A2005 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 ≤ t ≤ 13. how fast is the length changing at age t = 7 years?