Let $D$ be the intersection of $PS$, $QT$, and $RU$ of $\triangle{PQR}$ where $S$, $T$, and $U$ are points respectively on $QR$, $PR$ and $PQ$. If $DS=DT=DU=3$ and $PD+QD+RD=43$, then $PD.QD.RD=?$