[tex]\bf \begin{cases}
F = \{(0, 1), (\stackrel{x}{2}, \stackrel{y}{4}), (4, 6), (6, 8)\} & F(\stackrel{x}{2})=\stackrel{y}{4}
\\\\\\
G = \{(\stackrel{x}{2}, \stackrel{y}{5}), (4, 7), (5, 8), (6, 9), (7, 5)\} \qquad & G(\stackrel{x}{2})=\stackrel{y}{5}
\end{cases}
\\\\\\
(F\cdot G)(2)\implies F(2)\cdot G(2)\implies 4\cdot 5\implies 20[/tex]
