26.
\[
\lim_{n \to \infty} \sum_{k=1}^{n} \frac{k^2 + 2kn}{k^3 + 3k^2 n + n^3} \text{의 값은?} \quad [3 \text{점}]
\]

\begin{itemize}
    \item[1] $\ln 5$
    \item[2] $\frac{\ln 5}{2}$
    \item[3] $\frac{\ln 5}{3}$
    \item[4] $\frac{\ln 5}{4}$
    \item[5] $\frac{\ln 5}{5}$
\end{itemize}