Three moles of ammonia ($a=4.17{\mathrm{L}}^2\mathrm{atm}\mathrm{mo}{\mathrm{l}}^{-2}$, $b=0.0371\mathrm{L}\mathrm{mo}{\mathrm{l}}^{-1}$) are contained in a $2.0\mathrm{L}$ vessel at $400\mathrm{K}$ ($R=0.0821\mathrm{L}\mathrm{atm}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$). Which statements are correct?

1. AThe pressure correction term $a{n}^2/V^2$ is about $9.4\mathrm{atm}$
2. BThe free volume $V-nb$ is about $1.89\mathrm{L}$
3. CThe van der Waals pressure is about $42.8\mathrm{atm}$
4. DThe ideal gas pressure is lower than the van der Waals pressure