$2\mathrm{.}4$ A saturated soil specimen has $w=36\%$ and ${}_d=13\mathrm{.}5k\frac{N}{m^3}.$ Determine the specimen's $($a$)$ void ratio, $($b$)$ porosity, $($c$)$ specific gravity of soil solids, and $($d$)$ saturated unit weight $($in $k\frac{N}{m^3}).$