Equilibrium: JEE Mains 2022 June 29 Shift 2

$4.0$ moles of argon and $5.0$ moles of $\mathrm{PCl_5}$ are introduced into an evacuated flask of $100$ litre capacity at $610\ \text{K}$. The system is allowed to equilibrate. At equilibrium, the total pressure of the mixture was found to be $6.0\ \text{atm}$. The $K_p$ for the reaction $\mathrm{PCl_5\rightleftharpoons PCl_3+Cl_2}$ is [Given : $R=0.082\ \text{L atm K}^{-1}\text{mol}^{-1}$]