Hanoi Open Mathematics Competition 2009 Junior Question 9

Triangle $ABC$ has area $60\,\mathrm{cm}^2$. Points $R,S$ lie on $BC$ with $BR=RS=SC$, and $P,Q$ are the midpoints of $AB,AC$, respectively. Lines $PS$ and $QR$ meet at $T$. Find the area of triangle $PQT$.