Explanation

(d) Vander Waal’s gas constant $b = 4 \times$ total volume of all the molecules of the gas in the enclosure
Or $b = 4 \times N \times \frac{4}{3}\pi\left( \frac{d}{2} \right)^{3} = \frac{2}{3}\pi Nd^{3}$
$= \frac{2}{3} \times 3.14 \times 6.02 \times 10^{23} \times \left( 2.94 \times 10^{- 10} \right)^{3} = 32 \times 10^{- 6}\frac{m^{3}}{mol}$