the soil sample has a density of $1\mathrm{.}68$Mg$/$m$3,$ a water content of $40\%$ and a density of solid grains of $2\mathrm{.}7$Mg$/$m$3.$ Using the phase diagram $($do not use a known formula$),$ what are: a$)$the dry density of this soil? b$)$the degree of saturation? c$)$The void index?