\( 4.0 \) 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 mixture was found to be \( 6.0 \) atom. The \( K_p \) for the reaction is [Given: \( R = 0.082 \, \text{L atm K}^{-1} \text{ mol}^{-1} \) ]
