The porosity $(n)$ and the degree of saturation $(S)$ of a soil sample are 0.7 and $40 \%,$ respectively. In a $100 \mathrm{~m}^{3}$ volume of the soil, the volume (expressed in $\mathrm{m}^{3}$ ) of air is
The porosity $(n)$ and the degree of saturation $(S)$ of a soil sample are 0.7 and $40 \%,$ respectively. In a $100 \mathrm{~m}^{3}$ volume of the soil, the volume (expressed in $\mathrm{m}^{3}$ ) of air is