The completed frequency table is as follows:
\[
\begin{array}{|c|c|c|c|}
\hline
\text{Grade} & \text{Frequency} & \text{Relative Frequency (\%)} & \text{Cumulative Frequency} \\
\hline
A & 4 & 16.7 & 4 \\
B & 7 & 29.2 & 11 \\
C & 9 & 37.5 & 20 \\
D & 2 & 8.3 & 22 \\
F & 2 & 8.3 & 24 \\
\hline
\end{array}
\]
Thus, the final answer is boxed as follows:
\[
\boxed{\text{Frequency Table Completed}}
\]