Let \( P\left(\dfrac{2\sqrt{3}}{\sqrt{7}}, \dfrac{6}{\sqrt{7}}\right), Q, R \) and \( S \) be four points on the ellipse \( 9x^2 + 4y^2 = 36 \). Let \( PQ \) and \( RS \) be mutually perpendicular and pass through the origin. If \( \dfrac{1}{(PQ)^2} + \dfrac{1}{(RS)^2} = \dfrac{p}{q} \), where \( p \) and \( q \) are coprime, then \( p+q \) is equal to:
