What is the pressure of 2 moles of ${\mathrm{NH}}_3 \mathrm{at} {27}^0\mathrm{C}$ when its volume is 5 litre in van der Waals equation (a = 4.17, b = 0.03711) ?

$$\begin{gathered} \left(\mathrm{P}+\frac{{\mathrm{n}}^2\mathrm{a}}{{\mathrm{V}}^2}\right) \left(\mathrm{V}-\mathrm{nb}\right) = \mathrm{nRT} \\ \left(\mathrm{P} + \frac{{\left(2\right)}^2 \mathrm{x} 4.17}{{\left(5\right)}^2}\right) \left(5-2 \mathrm{x} .03711\right)= 2 \mathrm{x} .0821 \mathrm{x} 300 \\ \mathrm{P} = \frac{2 \mathrm{x} .0821 \mathrm{x} 300}{5-2 \mathrm{x} .03711} - \frac{4.7 \mathrm{x} 2^2}{5^2} \\ \Rightarrow 10-0.66 = 9.3 \mathrm{atm} \end{gathered}$$