[T] A version of von Bertalanffy growth can be used to estimate the age of an individual in a homogeneous species from its length if the annual increase in year $n+1$ satisfies $a_{n+1}=k\left(S-S_{n}\right), \quad$ with $S_{n}$ as the length at year $n, \quad S$ as a limiting length, and $k$ as a relative growth constant. If $S_{1}=3, \quad S=9,$ and $k=1 / 2,$ numerically estimate the smallest value of $n$ such that $S_{n} \geq 8$ . Note that $S_{n+1}=S_{n}+a_{n+1} .$ Find the corresponding $n$ when $k=1 / 4$ .