In a given figures, if $ABCD$ is a rectangle and $P,Q$ are the mid-points of $AD,DC$ respectively. Then, the ratio of lengths $PQ$ and $AC$ is equal to

In the given figure, $ABCD$ is a parallelogram in which $P$is the mid-point of $DC$ and $Q$is a point on $AC$ such that $CQ=\frac{1}{4}AC$and $PQ$product meet $BC$ at $R$, then,