Let \( R \) be the point \( (3,7) \) and let \( P \) and \( Q \) be two points on the line \( x+y=5 \) such that \( PQR \) is an equilateral triangle. Then the area of \( \triangle PQR \) :
\( \dfrac{25}{4\sqrt{3}} \)
\( \dfrac{25\sqrt{3}}{2} \)
\( \dfrac{25}{\sqrt{3}} \)
\( \dfrac{25}{2\sqrt{3}} \)