CAT 2017 Geometry & Mensuration — Previous Year Question

$ABCD$ is a rectangle. $P, Q$ and $R$ are the midpoint of $BC, CD$ and $DA$. The point $S$ lies on the line $QR$ in such a way that $SR:QS=1:3$. The ratio of the area of triangle $APS$ to area of rectangle $ABCD$ is