A gas obeys $P(V - b) = RT$. Which of the following are correct about this gas?

I. Isochoric curves have slope $= R/(V - b)$

II. Isobaric curves have slope $R/P$ and intercept $b$.

III. For the gas, compressibility factor $= 1 + Pb/RT$

IV. The attraction forces are overcome by repulsive forces.