A gas has a compressibility factor of 0.5 and a molar volume of 0.4 dm³ mol⁻¹ at a temperature of 800 K and pressure x atm. If it shows ideal gas behaviour at the same temperature and pressure, the molar volume will be y dm³ mol⁻¹. The value of x/y is ___. [Use: Gas constant, R = 8 × 10⁻² L atm K⁻¹ mol⁻¹]