Let the area of a \( \triangle PQR \) with vertices \( P(5, 4) \), \( Q(-2, 4) \) and \( R(a, b) \) be \( 35 \) square units. If its orthocenter and centroid are \( O\!\left(2, \dfrac{14}{5}\right) \) and \( C(c, d) \) respectively, then \( c + 2d \) is equal to:
