A uniform beam $(EI = \textit{constant})PQ$ in the form of a quarter-circle of radius $R$ is fixed at end $P$ and free at the end $Q$, where a load $W$ is applied as shown. The vertical downward displacement, $\delta_q$, at the loaded point $Q$ is given by: $\delta_q = \beta \bigg( \dfrac{WR^3}{EI} \bigg)$. Find the value of $\beta$(correct to $4$-decimal places). ______