Use summation notation $to$ rewrite the given sum $in$ terms $ofk.$

$\frac{5}{8*9}+\frac{6}{9*10}+$cdots$+\frac{n}{(n+3)(n+4)}$

Select the correct expression.

${\displaystyle \underset{k=5}{\overset{n}{}}}\frac{n}{(n+3)(n+4)}$

${\displaystyle \underset{k=5}{\overset{k}{}}}\frac{n}{(n+3)(n+4)}$

${\displaystyle \underset{k=5}{\overset{n}{}}}\frac{k}{(k+3)(k+4)}$

${\displaystyle \underset{k=1}{\overset{}{}}}\frac{k}{(k+3)(k+4)}$

${\displaystyle \underset{k=5}{\overset{}{}}}\frac{k}{(k+3)(k+4)}$