$\text{PCl}_5$ dissociates as
$\text{PCl}_5(\text{g}) \rightleftharpoons \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g})$
5 moles of $\text{PCl}_5$ are placed in a 200 litre vessel which contains 2 moles of $\text{N}_2$ and is maintained at 600 K. The equilibrium pressure is 2.46 atm. The equilibrium constant $\text{K}_\text{p}$ for the dissociation of $\text{PCl}_5$ is $\underline{\qquad} \times 10^{-3}$. (nearest integer)
(Given : $\text{R} = 0.082 \text{ L atm K}^{-1}\text{ mol}^{-1}$; Assume ideal gas behaviour)