Square pyramid $ABCDE$ has base $ABCD$, which measures $3$cm on a side, and altitude $\overline{AE}$ perpendicular to the base which measures $6$cm. Point $P$ lies on $\overline{BE}$, one third of the way from $B$ to $E$; point $Q$ lies on $\overline{DE}$, one third of the way from $D$ to $E$; and point $R$ lies on $\overline{CE}$, two thirds of the way from $C$ to $E$. What is the area, in square centimeters, of $\triangle{PQR}$?