${\mathrm{XY}}_2$dissociates as: ${\mathrm{XY}}_{2\left(\mathrm{g}\right)}\rightleftharpoons \mathrm{XY}\left(\mathrm{g}\right)+\mathrm{Y}\left(\mathrm{g}\right)$.Initial pressure of${\mathrm{XY}}_2$ is 600 mm Hg. The total pressure at equilibrium is 800 mm Hg. Assuming volume of system to remain constant, the value of Kp is