2. Given that $x, y, z$ satisfy the system of equations
$$
\left\{\begin{array}{l}
x^{2}+x y+\frac{1}{3} y^{2}=25, \\
z^{2}+\frac{1}{3} y^{2}=9, \\
x^{2}+z x+z^{2}=16 .
\end{array}\right.
$$

Find the value of $x y+2 y z+3 x z$.
(17th All-Russian High School Mathematics Competition)
(Hint: Construct a triangle. Answer: $24 \sqrt{3}$ )