JEE Advanced 2023 Chemistry question on States of Matter

A gas has a compressibility factor of 0.5 and a molar volume of 0.4 dm$^3$ 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 dm$^3$ mol$^{-1}$. The value of $\textbf{x/y}$ is ___.

[Use: Gas constant, R = 8 $\times$ 10$^{-2}$ L atm K$^{-1}$ mol$^{-1}$]