A partially-saturated soil sample has natural moisture content of $25\%$ and bulk unit weight of $\text{18.5 kN/m}^3$. The specific gravity of soil solids is $2.65$ and unit weight of water is $\text{9.81 kN/m}^3$. The unit weight of the soil sample on full saturation is

1. $\text{21.12 kN/m}^3$
2. $\text{19.03 kN/m}^3$
3. $\text{20.12 kN/m}^3$
4. $\text{18.50 kN/m}^3$