\end{center}

         Câu a)

\begin{center}
	\begin{tabular}{l | llll}
		\textbf{~~~} & \textbf{A} & \textbf{B} & \textbf{C} & \textbf{D}\\
		\hline
		$\mathcal{Q}_1(AB)$ & $a$ & $b$ & $c_1$ & $d_1$\\
		$\mathcal{Q}_2(AC)$ & $a$ & $b_2$ & $c$ & $d_2$ \\
		$\mathcal{Q}_3(BD)$ & $a_3$ & $b$ & $c_3$ & $d$ \\
	\end{tabular}
\\
Apply \fd{A}{B}
\\
	\begin{tabular}{l | llll}
		\textbf{~~~} & \textbf{A} & \textbf{B} & \textbf{C} & \textbf{D}\\
		\hline
		$\mathcal{Q}_1(AB)$ & $a$ & $b$ & $c_1$ & $d_1$\\
		$\mathcal{Q}_2(AC)$ & $a$ & $b_2$ & $c$ & $d_2$ \\
		$\mathcal{Q}_3(BD)$ & $a_3$ & $b$ & $c_3$ & $d$ \\
	\end{tabular}
\end{center}