The partial pressures in an equilibrium mixture of NO, $Cl_{2}$ and $NOCl$ at 500 $K$ are as follows: $P_{\mathrm{NO}}=0.240 \mathrm{atm} ;$ $P_{Cl_{2}}=0.608 \mathrm{atm} ; P_{\mathrm{NOCl}}=1.35 \mathrm{atm} .$ What is $K_{\mathrm{p}}$ at 500 $K$ for the reaction $2 NO(g)+\mathrm{Cl}_{2}(g) \rightleftharpoons 2 \mathrm{NOCl}(g) ?$