$PQRS$ is a square. The points $T$ and $U$ are the midpoints of $QR$ and $RS$ respectively. The line $QS$ cuts $PT$ and $PU$ at $W$ and $V$ respectively. What fraction of the area of the square $PQRS$ is the area of the pentagon $RTWVU$?
(A) $\dfrac{1}{3} \quad$ (B) $\dfrac{2}{5} \quad$ (C) $\dfrac{3}{7}\quad$ (D) $\dfrac{5}{12}\quad$ (E) $\dfrac{4}{15}$